Aromatic Hydrocarbon Separation via Extractive Distillation and Liquid-Liquid Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for separating aromatic hydrocarbons, such as liquid-liquid extraction and extractive distillation, face challenges in achieving high purity and recovery rates while maintaining low energy consumption, especially when processing wide fractions like C6-C8 hydrocarbon mixtures, leading to increased energy consumption and impurity levels.
Innovation Solution
A combined process of extractive distillation and liquid-liquid extraction is implemented, where a hydrocarbon mixture is introduced to the middle of an extractive distillation column with an extraction solvent, followed by liquid-liquid extraction and solvent recovery, optimizing benzene evaporation and recycling to achieve high purity aromatic hydrocarbons with reduced energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If liquid-liquid extraction method is used to separate aromatic hydrocarbons from wide fractions, then high purity BTX can be obtained, but energy consumption increases significantly due to large amount of backwashing liquids
Solution Approach 1:
The patent combines extractive distillation and liquid-liquid extraction into a hybrid process. The extractive distillation column performs preliminary separation to concentrate aromatic hydrocarbons in the bottoms stream, which then feeds into a smaller liquid-liquid extraction column. This merging allows the system to achieve high purity (99.9% BTX) while reducing the extraction column size and backwashing liquid requirements compared to using liquid-liquid extraction alone on wide fractions.
2Use of energy by moving object
If extractive distillation is used to treat wide fractions like C6-C8, then process simplicity and low energy consumption are achieved, but aromatic hydrocarbon purity is limited to 99.0-99.5% due to C8+ cycloalkane impurities
Solution Approach 1:
The patent segments the separation process into two distinct stages: first, extractive distillation separates the wide fraction into a raffinate stream (non-aromatics) and a bottoms stream (aromatic-enriched); second, a liquid-liquid extraction stage further purifies the aromatic hydrocarbons by removing C8+ cycloalkane impurities. This segmentation allows each unit to be optimized for its specific function, achieving both energy efficiency and high purity (99.9% BTX).
Solution Approach 2:
The patent introduces a solvent (such as sulfolane, N-methyl-2-pyrrolidone, or triethylene glycol) as an intermediary substance that selectively interacts with aromatic hydrocarbons. The solvent is fed into the extractive distillation column and enhances the relative volatility differences, enabling effective separation of aromatic hydrocarbons from non-aromatics in the wide fraction while maintaining energy efficiency.
3Manufacturing precision
If liquid-liquid extraction is applied to high aromatic content raw materials, then high purity products are obtained, but large amount of backwashing liquids must be evaporated, increasing energy consumption
Solution Approach 1:
The patent applies preliminary extractive distillation to pre-concentrate aromatic hydrocarbons before the liquid-liquid extraction step. This preliminary action reduces the volume of feed to the extraction column and decreases the amount of backwashing liquid generated, thereby reducing the energy required for evaporation while still achieving high purity aromatic hydrocarbon products.
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
The method achieves aromatic hydrocarbon purities of 99.0% or more with low energy consumption, effectively reducing C8 cycloalkane impurities and enhancing benzene recovery, meeting market specifications while minimizing energy expenditure.
Implementation Method 1
introducing a hydrocarbon mixture containing aromatic hydrocarbons into the middle of an extractive distillation column; introducing an extraction solvent into the upper part of the extractive distillation column; after an extractive distillation
Implementation Method 2
the raffinate discharged from the top of the extractive distillation column is sent to the lower part of an extraction column; the extraction solvent is introduced to the upper part of the extraction column; after a liquid-liquid extraction
Implementation Method 3
the rich solvent obtained from the bottom of the extractive distillation column is sent to the middle of a solvent recovery column; after vacuum distillation, the aromatic hydrocarbons are discharged from the top of the solvent recovery column
Data Source
AI summary
A method for separating aromatic hydrocarbons by an extractive distillation, comprising introducing a hydrocarbon mixture containing aromatic hydrocarbons into the middle of an extractive distillation column (8); introducing an extraction solvent into the upper part of the extractive distillation column; after an extractive distillation, a raffinate containing benzene is discharged from the top of the column, wherein the benzene content is 3-40% by mass, and sent to the lower part of the extraction column (10); the extraction solvent is introduced to the upper part of the extraction column for a liquid-liquid extraction; a raffinate liquid free of aromatic hydrocarbons is discharged from the top of the extraction column; a rich solvent containing benzene is discharged from the bottom of the column and enters the upper-middle part of the extractive distillation column; the rich solvent obtained at the bottom of the extractive distillation column is sent to the solvent recovery column to separate the aromatic hydrocarbons and the solvent. By combining an extractive distillation with a liquid-liquid extraction ingeniously, the method can achieve the separation of aromatic hydrocarbons with a high purity and a high recovery rate, and a significant decrease of the energy consumption in the extraction and separation process.