Extractive Distillation Solvent Purification for Co-Boiler Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for purifying solvents used in extractive distillation are inefficient in removing impurities with similar boiling points to the solvent, leading to reduced extraction power and increased costs due to frequent solvent replacement, especially in processes producing benzene, toluene, and xylene.
Innovation Solution
A method involving liquid-liquid extraction with an aliphatic extraction solvent to remove impurities from the solvent, followed by distillation of the aqueous phase to recover the solvent, reducing the need for water addition and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If distillation is used to purify the solvent, then impurities with higher boiling points are removed, but impurities with similar boiling points (co-boilers) remain in the solvent
Solution Approach 1:
The patent applies liquid-liquid extraction to remove co-boiler impurities from the solvent. An extraction agent is introduced that selectively extracts co-boiler impurities (impurities with similar boiling points to the solvent) from the solvent phase, separating them into an extract phase. This allows removal of impurities that conventional distillation cannot separate due to their similar volatility, thereby maintaining solvent extraction power and purity.
2Manufacturing precision
If water is added to purify the solvent by distillation, then the solvent can be recovered, but large amounts of energy are consumed for distillation
Solution Approach 1:
The patent introduces an extraction agent as an intermediary substance to facilitate impurity removal. Instead of directly distilling the solvent (which requires high energy), the extraction agent mediates the separation process by selectively binding to co-boiler impurities, allowing them to be removed in the extract phase. This indirect approach through an intermediary reduces the energy burden compared to direct distillation while achieving effective purification.
3Productivity
If the solvent cycle continues without purification, then resource consumption is reduced, but impurities accumulate and extraction power is lost
Solution Approach 1:
The patent implements a selective discarding and recovering strategy. The solvent cycle continues operating, but when co-boiler impurities accumulate to affect extraction power, the system selectively discards only the contaminated portion (extract phase containing impurities) while recovering and recycling the purified solvent (raffinate phase). This maintains continuous productivity while preserving solvent reliability by removing only the necessary contaminated fraction rather than replacing the entire solvent inventory.
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 process effectively purifies the solvent without adding water, maintaining its selectivity and capacity, suitable for anhydrous aromatic production, and reduces resource and energy costs.
Implementation Method 1
liquid-liquid extraction with an aliphatic extraction solvent to remove impurities from the solvent
Implementation Method 2
liquid-liquid extraction between the partial stream and an extraction agent for aliphatics
Implementation Method 3
distillation of the aqueous phase to recover the solvent
Implementation Method 4
separating the aqueous phase from the hydrophobic phase and distilling the aqueous phase to remove the water
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a method for separating a hydrocarbon-containing feedstock stream (1) by extractive distillation, wherein: the feedstock stream (1) is brought into contact (110) with a water-soluble solvent (4) for aromatics in a counterstream; an aliphatic-compounds fraction is distillatively separated (120) from the obtained mixture (5) as an aliphatic-compounds product stream (2); the aromatics are stripped (130) from the remaining aromatics-enriched solvent (6); and the aromatics-depleted solvent (4) is fed back (140) in a solvent circuit (7); wherein: aliphatic compounds and/or compounds which have aliphatic functional groups collect as impurities in the solvent circuit (7) and at least one partial stream (8) of the solvent circuit (7) is purified (150) to remove the impurities; wherein: for the purification (150), a liquid-liquid extraction is carried out between the partial stream (8) and an extraction agent (9) for aliphatic compounds and the raffinate (10) of the liquid-liquid extraction is fed back into the solvent circuit (7). The invention also relates to a device for carrying out the method.