KR102318324B1 - Flexible process for enhancing steam cracker and platforming feedstocks - Google Patents

Abstract

Methods are provided for either increasing the yield of light olefins or shifting the hydrocarbon component from a hydrocarbon feedstock to a gasoline blending pool. The method includes separating the naphtha feedstock into a component in a first stream that is more readily processed in a cracking unit and a component in a second stream that is more readily processed in a reforming unit. The method includes the ability to convert a component from a cracking stream to a reforming stream and converting a component from a reforming stream to a cracking stream.

Description

FLEXIBLE PROCESS FOR ENHANCER STEAM CRACKER AND PLATFORMING FEEDSTOCKS

STATEMENT OF PRIORITY

This application claims the benefit of U.S. Provisional Application No. 61/863,019, filed on August 7, 2013, the contents of which are incorporated herein by reference in their entirety, of U.S. Application Serial No. 14/260,812, filed April 24, 2014; claim priority.

field of invention

The present invention relates to a process and system for the production of aromatics from heavier hydrocarbon streams. Specifically, this process provides increased yield and flexibility for producing aromatics and light olefins from hydrocarbon feedstocks.

Reforming of petroleum raw materials is an important process for the production of useful products. One important process is the separation and upgrading of hydrocarbons for automotive fuels, such as the production of naphtha feedstreams in the production of gasoline and the upgrading of the octane number of naphtha. However, hydrocarbon feedstreams from crude oil sources include the production of useful chemical precursors for use in the manufacture of plastics, detergents and other products.

Gasoline upgrading is an important process, and improvements in conversion of naphtha feedstreams to increase octane number are described in US Pat. Nos. 3,729,409; 3,753,891; 3,767,568; 4,839,024; 4,882,040; and 5,242,576. These processes involve various means for improving the octane number, especially the aromatic content of gasoline.

The process involves splitting the feed and operating several reformers using different catalysts such as monometal catalysts or non-acid catalysts for low boiling hydrocarbons and bimetal catalysts for high boiling hydrocarbons. Other improvements are described in US Pat. Nos. 4,677,094; 6,809,061; and new catalysts as set forth in No. 7,799,729. However, the methods and catalysts presented in these patents have limitations that may entail a significant increase in cost.

Light olefins have conventionally been produced via processes of steam or catalytic cracking and include ethylene and propylene. Light olefins are also derived from the same feedstock as gasoline. Due to limited availability and high cost of petroleum sources, the cost of producing light olefins from such petroleum sources is steadily increasing. The ability to shift components in feedstocks for light olefins and gasoline pools allows manufacturers to economically select the most important production lines and to shift some of the hydrocarbon components in an efficient manner.

A method for improving the yield and providing flexibility of reformate, a light olefin, in the processing of naphtha is presented. A first embodiment of the present invention is a process for increasing light olefins and reformate yields, wherein a first portion of a hydrocarbon feed stream is passed through a fractionation column to an overhead stream comprising C6 compounds and lighter components, and a heavier generating a bottom stream comprising phosphorus hydrocarbons; passing the overhead stream through a cracking unit; passing the bottom stream through a separation unit to produce an extract stream comprising normal hydrocarbons and a raffinate stream comprising non-normal hydrocarbons; and passing the extract stream through a cracking unit to produce light olefins.

A second embodiment of the present invention is a process for increasing light olefins yield, wherein a hydrocarbon stream is passed through a fractionation column to provide a first overhead stream comprising nC4 and lighter hydrocarbons and a second overhead stream comprising C5 and heavier hydrocarbons. 1 generating a bottom stream; passing the first bottom stream through a separation unit to produce an extract stream comprising normal hydrocarbons and a raffinate stream comprising non-normal hydrocarbons; passing the raffinate stream through a reforming unit to produce a reformate stream; and passing the extract stream through a cracking unit to produce light olefins. Embodiments of the present invention pass a raffinate stream through a raffinate separation system to provide a second overhead stream comprising C5 and C6 hydrocarbons, an intermediate stream comprising C7 and heavier alkanes, and C6 and heavier aromatics and any, any, or all of the previous embodiments of this paragraph through the second embodiments of this paragraph, further comprising generating a second bottom stream comprising naphthenes and a desorbent.

A third embodiment of the present invention is a process for providing flexibility in gasoline production, wherein the hydrocarbon stream is passed through a fractionation column to include a first overhead stream comprising nC4 and lighter hydrocarbons and C5 and heavier hydrocarbons. generating a first bottom stream to passing the first bottom stream through a hydrogenation unit to produce a treated bottom stream with reduced acetylene, diolefin, sulfur and nitrogen content; passing the treated bottom stream through a separation unit to produce an extract stream comprising normal hydrocarbons and a raffinate stream comprising non-normal hydrocarbons; passing the raffinate stream through a reforming unit to produce a reformate stream; and passing a portion of the extract stream through a cracking unit to produce light olefins. Embodiments of the present invention pass an extract stream through an extract separation system to provide a second overhead stream comprising C5 and C6 normal alkanes, an intermediate stream comprising C7 and heavier normal alkanes, and a second comprising desorbent one, any or all of the previous embodiments of this paragraph through the third embodiments of this paragraph, further comprising generating a bottom stream.

In one embodiment, the method comprises the use of an isomerization unit to convert a C5-C6 stream. The isomerization unit can be used to convert the iC5-iC6 stream to a mixture of iC5-iC6 and normal C5 and C6 components to increase the yield of light olefins. Alternatively, to increase the yield for the gasoline pool, a stream of nC5-nC6 may be passed through an isomerization unit to convert the stream to a mixture of iC5-iC6 and normal C5 and C6 components.

Other objects, advantages and applications of the present invention will become apparent to those skilled in the art from the following detailed description and drawings.

1 is a basic case illustrating a process for splitting a naphtha stream between a feed to a cracking unit and a feed to a reforming unit;
2 is an embodiment illustrating separation of a naphtha splitter bottom stream to increase light olefin yield;
3 is an embodiment illustrating separation of a naphtha splitter bottom stream using isomerization to increase light olefin yields;
4 is an embodiment illustrating the separation of a naphtha splitter bottom stream using isomerization to increase gasoline blending pool yield.

Methods are provided for either increasing the yield of light olefins or shifting the hydrocarbon component from a hydrocarbon feedstock to a gasoline blending pool. The method comprises separating a naphtha feedstock into a component in a first stream or cracking unit stream that is more readily processed in a cracking unit, and a second stream or component in a reforming unit feedstream that is more readily processed in a reforming unit. includes steps. The method includes the ability to convert a component from a cracking stream to a reforming stream and converting a component from a reforming stream to a cracking stream.

Processing of the naphtha feedstream can be used to produce light olefins and to provide a hydrocarbon component for a gasoline blending pool or reforming component to produce aromatics for passage through the aromatics complex. The basic process as shown in FIG. 1 involves splitting the naphtha feed stream into two parts, a second part ( 6 ) and a first part ( 8 ). The amount of the second portion may be as little as zero, depending on the choice of product, or may include all of the naphtha feedstream. A second portion (6) is passed through a cracking unit (20) to produce a process stream (22) having light olefins. Light olefins include ethylene and propylene. A first portion (8) of the naphtha feed stream is passed through a naphtha splitter (10) to produce an overhead stream (12) and a bottom stream (14). Overhead stream 12 comprises C6 and lighter components in the naphtha feed stream. Bottom stream 14 contains C6 and heavier components in the naphtha feed stream. Typical ranges for the heavier components are C5 to C11 hydrocarbons. Splitter 10 operates based on the relative boiling points of the hydrocarbon components, and splitter overhead stream 12 may include components having boiling points less than or equal to methyl cyclopentane (MCP). To adjust the desired overhead composition, including changing the operating conditions to have an overhead stream 12 comprising C4 and lighter components and a bottom stream 14 comprising C5 and heavier components. The operating conditions can be changed. The overhead stream 12 is passed through a cracking unit 20 . The bottom stream 14 is passed through a hydrogen treatment unit 30 to produce a treated stream 32 . The treated stream 32 is passed through a reforming unit 40 to produce a reformate stream 42 with increased aromatics content.

The normal component in the hydrocarbon stream is more readily decomposed to form olefins that are lighter than the non-normal component. Normal components are more difficult to reform into aromatics than non-normal components. In addition, branched paraffin is a preferred component for gasoline blending pools compared to the normal component. Separation of normal and non-normal components combined with passing different streams through appropriate downstream processing units improves the flexibility and economics of cracking and reforming naphtha. The ability to convert normal components to non-normal components enables the movement of hydrocarbon components from the stream fed to the cracking unit into a stream for producing gasoline components.

In one embodiment, as shown in FIG. 2 , the method is for increasing light olefins and reformate yields. The process passes a first portion (8) of a hydrocarbon feed stream through a fractionation column (10) to an overhead stream (12) comprising C6 and lighter components, and a bottom stream (14) comprising heavier components. ) to create An overhead stream (12) is passed through a cracking unit (20) to produce a process stream (22) comprising light olefins. The bottom stream 14 is passed through a hydrogen treatment unit 30 to produce a treated bottom stream 32 . Hydrotreating unit 30 removes impurities to protect downstream catalysts and adsorbents. The removed impurities include sulfur compounds and nitrogen compounds. Also, some hydrogenated hydrocarbon compounds such as acetylenes and diolefins may be present. These are more reactive compounds, and hydrogenation of these compounds can reduce some downstream side reactions such as polymerization.

The treated bottom stream (32) is passed through a separation unit (50) to produce an extract stream (52) and a raffinate stream (54). Separation unit 50 is preferably an adsorptive separation unit and includes an adsorbent to selectively adsorb components from the treated bottom stream. In one embodiment, the adsorbent is selected to preferentially adsorb normal components from stream 32 while excluding non-normal components. Extract stream 52 comprises normal hydrocarbons in the range of C5 to C11 and raffinate stream 54 comprises non-normal components from the bottom stream. Non-normal components include branched-chain paraffins, naphthenes and aromatic compounds. Extract stream 52 is passed through cracking unit 20 to increase the yield of light olefins from the hydrocarbon feed stream. In one embodiment, the hydrocarbon feedstream is a naphtha feedstream. Although this embodiment is illustrated by a naphtha feedstream, the process is not limited to the naphtha feedstream and may include any feedstream having a composition that overlaps with the naphtha feedstream. For a naphtha feed stream, cracking unit 20 may be a naphtha steam cracking unit.

In one embodiment, the method further comprises passing the raffinate stream 54 through a reforming unit 40 to produce a reformate stream 42 with increased aromatic content.

The method may further comprise passing a second portion (6) of the hydrocarbon feed stream through a cracking unit (20).

The use of naphtha for the production of ethylene and propylene is common. It is known that normal paraffin and n-paraffin are preferred because they are relatively easy to decompose compared to non-normal paraffin. Likewise, naphtha is used as part of a gasoline blending pool or as a feedstock for reforming to produce aromatics that can be used in an aromatics complex. Non-normal paraffin is also a useful ingredient in gasoline blending pools or reforming. Improving the ability to convert naphtha feedstocks for the production of light olefins or for the production of gasoline or aromatics can improve the economics of refineries.

In one embodiment, as shown in FIG. 3 , the method provides an improvement in light olefin yield. The process comprises passing a hydrocarbon feed stream (8) through a fractionation unit (10). Fractionation unit 10 produces an overhead stream 12 comprising C4 and lighter hydrocarbon components, and a bottom stream 14 comprising C5 and heavier components. An overhead stream (12) is passed through a cracking unit (20) to produce a process stream (22) having light olefins. The bottom stream 14 is passed through a hydrogen treatment unit 30 to produce a treated bottom stream 32 . The treated bottom stream 32 is passed through a separation unit 50 to produce an extract stream 52 comprising normal hydrocarbons and a raffinate stream 54 comprising non-normal hydrocarbons. Non-normal hydrocarbons include branched-chain paraffins, naphthenes and aromatics. The extract stream 52 is passed through a cracking unit 20 .

Raffinate stream 54 is passed through raffinate separation system 60, producing a raffinate overhead stream 62, an intermediate raffinate stream 64, and a raffinate bottom stream 66. Separation unit 50 includes an adsorptive separation system and includes the use of a desorbent as a working fluid in an adsorptive separation process. The raffinate bottom stream 66 contains the desorbent and is recycled back to the separation unit 50 . The intermediate raffinate stream comprises non-normal C7 to C11 paraffins, and C6 to C11 aromatic and naphthenic components in the raffinate stream. Raffinate overhead stream 62 comprises iC5 and iC6 components from the raffinate stream.

The raffinate overhead stream 62 is passed through an isomerization unit 70 to produce an isomerate stream 72 . Isomerization unit 70 includes a contact reactor that receives a mixture of hydrocarbon components and isomerizes the components to produce a new composition for isomer stream 72 . The isomerization process can convert branched-chain paraffins to normal paraffins, or can be used to convert normal paraffins to branched-chain paraffins. In this embodiment, the feed to the isomerization unit will consist of branched-chain paraffins and will produce a mixture of branched-chain and normal paraffins. The isomer stream 72 is passed through a separation unit 50 . This embodiment increases the amount of normal paraffin produced and increases the feed to the cracking unit 20 . Increasing the feed of normal paraffins to the cracking unit increases the amount of light olefins produced for cracking process stream 22 .

In one embodiment, as shown in FIG. 4 , the method provides the flexibility to increase gasoline production or increase aromatics production. The process comprises passing a hydrocarbon feed stream (8) through a fractionation unit (10). Fractionation unit 10 produces an overhead stream 12 comprising C4 and lighter hydrocarbon components, and a bottom stream 14 comprising C5 and heavier components. An overhead stream (12) is passed through a cracking unit (20) to produce a process stream (22) having light olefins. The bottom stream 14 is passed through a hydrogen treatment unit 30 to produce a treated bottom stream 32 . The treated bottom stream 32 is passed through a separation unit 50 to produce an extract stream 52 comprising normal hydrocarbons and a raffinate stream 54 comprising non-normal hydrocarbons. Non-normal hydrocarbons include branched-chain paraffins and olefins, naphthenes and aromatics.

Raffinate stream 54 is passed through raffinate separation system 60, producing a raffinate overhead stream 62, an intermediate raffinate stream 64, and a raffinate bottom stream 66. Separation unit 50 includes an adsorptive separation system and includes the use of a desorbent as a working fluid in an adsorptive separation process. The raffinate bottom stream 66 contains the desorbent and is recycled back to the separation unit 50 . The intermediate raffinate stream comprises non-normal C7 to C11 paraffins and C6 to C11 aromatic and naphthenic components in the raffinate stream. The raffinate overhead stream 62 includes iC5 and iC6 components in the raffinate stream that is later passed to a gasoline blending pool, or some other downstream process.

The extract stream 52 is passed through an extract separation system 80 , producing an extraction overhead stream 82 , an intermediate extract stream 84 and an extract bottom stream 86 . The extract bottom stream 86 contains the desorbent and is recycled to the adsorptive separation unit 50 . Extract intermediate stream 84 comprises C7 to C11 normal paraffins and is passed through cracking unit 20 to produce light olefins.

Extract overhead stream 82 comprises nC5 and nC6 paraffins and is passed through isomerization unit 70 to produce isomerization process stream 72 . Isomerization process stream 72 is passed through separation unit 10 to convert the stream of normal paraffins to a mixture of normal and branched chain paraffins. This embodiment increases the amount of branched paraffin and increases the amount of raffinate from the separation unit 10 . This provides an increase in iC5 and iC6, resulting in an increase in the raffinate overhead stream 62, or an increase in feed to the gasoline blending pool.

The extract separation system and/or the raffinate separation system may comprise one or more separation columns for separating each extract or raffinate stream into a plurality of streams. Options for extract separation and/or raffinate separation systems include dividing wall columns or other means for separation of hydrocarbon streams.

It can be seen from the following results that there was a substantial increase in the normal content and the aromatic content with the addition of the separation unit 10 . This promotes increasing light olefins for cracking. It has been shown that addition of isomerization can also increase normals and aromatics. This provides a useful improvement on existing installations.

Comparison of cases Explanation normal(%) N+2A case 1 Base Case - No Separation Unit 26 57 case 2 With separation unit 59 71 case 3 With separation and isomerization 94 73

Case 1 provides a comparison of the standard processing used in industry today, in which straight run naphtha is fed to a steam cracker with minimal production. Direct current naphtha can be combined with the light ends from individual naphtha streams, which is a process for a catalytic reforming unit. The normal in the naphtha is typically in the range of 15% to 30% by weight. With the addition of a separation unit, separation can increase the amount of normal for the feed to the cracking unit as shown in case 2 . The addition of the isomerization unit enables further improvement of the quality of the feed to the digestion unit and reforming unit. The quality of the feed to the reforming unit (N+2A, or aromatic potential) shows that this treatment improves the yield from the reforming unit.

The addition of an isomerization unit also allows the plant operator to control the feed to the cracking unit or reforming unit, but allows additional flexibility by varying the quality of the hydrocarbons. The isomerization unit makes it possible to increase the amount of iC5 and iC6 forms of branched chain paraffin or the amount of normal.

While the present invention has been described using the presently contemplated preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various modifications and equivalent arrangements covered by the appended claims.

Claims (10)

A method for increasing light olefin and reformate yields, comprising:
passing a first portion of the hydrocarbon feed stream through a fractionation column to produce an overhead stream comprising C6 compounds and lighter components, and a bottom stream comprising heavier hydrocarbons;
passing the overhead stream through a cracking unit;
passing the bottom stream through a separation unit to produce an extract stream comprising normal hydrocarbons and a raffinate stream comprising non-normal hydrocarbons;
passing the extract stream through a cracking unit to produce light olefins;
passing the raffinate stream through a reforming unit to produce a reformate stream comprising aromatics;
Passing the reformate stream through the reformate separation system, a second overhead stream comprising C5 and C6 hydrocarbons, an intermediate stream comprising C7 and heavier alkanes, C6 and heavier aromatics and naphthenes, and a desorbent generating a second bottom stream including; and
recycling the second bottom stream comprising the desorbent to the separation unit;
An increase method comprising a. The process of claim 1 wherein the hydrocarbon feed stream is naphthine. According to claim 1,
passing the bottom stream through a hydrogen treatment unit to produce a treated bottom stream; and
passing the treated bottom stream through a separation unit;
An increase method further comprising a. The method of claim 1 , wherein the separation unit is an adsorptive separation unit. delete delete The method of claim 1 , further comprising passing a second portion of the hydrocarbon feed stream through a cracking unit. The method of claim 1 , wherein the cracking unit is a naphtha steam cracking unit. The process of claim 1 further comprising passing a portion of the raffinate stream through an isomerization unit to produce an isomerization process stream comprising isoparaffins and normal paraffins. 10. The process of claim 9 further comprising passing the isomerization process stream through a separation unit and passing the normal paraffins through a cracking unit.

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