TOL/A9+ Transalkylation Effluent Separation via Prefractionation

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Solution Overview

Problem

The energy-intensive separation of effluent from TOL/A9+ transalkylation reactors into streams concentrated in light ends, benzene, toluene, and C9+ aromatics poses a significant challenge, leading to high variable costs in aromatics complexes.

Innovation Solution

A process involving a prefractionation column and a sidedraw column to separate the effluent into streams rich in toluene, C8 aromatics, and C9+ aromatics, with the option to recycle A9+ back to the reactor, and a benzene column to recover paraxylene, reducing the need for additional fractionation and energy consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional separation methods are used to separate reactor effluent into streams concentrated in light ends, benzene, toluene, and C9+ aromatics, then the separation is achieved, but energy consumption is high

Engineering Contradiction:

Improveenergy consumptionVSAvoidseparation process complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The separation process is divided into two main segments: a prefractionation column that performs initial separation of the effluent stream, and a sidedraw column that completes the separation to produce the desired concentrated streams. This segmentation allows each column to be optimized for its specific separation task, reducing overall energy consumption compared to a single complex separation system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The prefractionation column performs preliminary separation of the effluent stream before it enters the sidedraw column. By removing lighter components and organizing the feed stream in advance, the sidedraw column operates more efficiently with reduced energy requirements to achieve the final separation into concentrated streams.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If separate A9 columns are used for fractionation, then complete separation is achieved, but capital costs increase

Engineering Contradiction:

Improveseparation purityVSAvoidnumber of columns

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The functionality of what would traditionally require separate A9 columns is merged into a single sidedraw column configuration. The sidedraw column is designed to simultaneously produce streams concentrated in toluene, C8 aromatics, and C9+ aromatics in one integrated unit, eliminating the need for multiple separate fractionation columns while maintaining the required separation purity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The sidedraw column is designed as a multi-functional unit that can produce multiple different concentrated streams (toluene-rich, C8 aromatics-rich, and C9+ aromatics-rich) from a single feed stream. This universal capability replaces what would otherwise require multiple specialized columns, reducing capital costs while maintaining separation precision.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables energy-efficient separation of reactor effluent into streams suitable for recycling and further processing, reducing energy and capital costs by eliminating the need for separate A9 columns and minimizing energy expenditure.

Implementation Method 1

providing a prefractionation column feed stream including toluene, C8 aromatics, and C9+ aromatics to a reboiled prefractionation column to produce a prefractionation column top stream and a prefractionation column bottom stream

Methodology Applied

Scientific EffectFractional distillation: Distillation

Implementation Method 2

providing the prefractionation column top stream and the prefractionation column bottom stream to a sidedraw column to produce a sidedraw column top stream including toluene, and a sidedraw column first side stream including C8 aromatics

Methodology Applied

Scientific EffectDistillation: Distillation

Data Source

PatentEP3105201B1Energy efficient fractionation process for separating the reactor effluent from TOL/a9+ translakylation processes

Publication Date: 2019.09.18 BP CORP NORTH AMERICA INC

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AI summary

Processes and apparatus are disclosed for the energy efficient separation of the effluent from a TOL/A9+ transalkylation reactor. The apparatus includes a reboiled prefractionation column and a sidedraw tower that produces: 1) an overhead stream including unreacted toluene, 2) a stream including unreacted C9+ aromatics, a portion of which stream may be recycled to the reactor; and 3) a sidedraw stream including C8 aromatics that may be directed to a crystallization or selective adsorption paraxylene separation unit for recovery o a paraxylene product.