Simulated Moving Bed Adsorption for p-Xylene Separation
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Solution Overview
Problem
Conventional simulated moving bed (SMB) adsorptive separation processes for p-xylene from aromatic hydrocarbon mixtures face limitations in improving productivity due to low initial concentration of p-xylene in the feed mixture, which restricts the desired separation efficiency.
Innovation Solution
A SMB adsorptive separation process that includes a pretreatment step in a single adsorption chamber to increase the concentration of p-xylene in the feed mixture before the main separation, utilizing a device with multiple adsorption chambers and rotary valves to simulate counterflow, enhancing the separation efficiency and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional batch chromatography is used for separation, then high purity separation can be achieved, but it requires a large amount of solvent and is not suitable for continuous separation in massive amount
Solution Approach 1:
The patent applies preliminary action by introducing a pretreatment step before the main SMB separation process. The pretreatment column pre-concentrates p-xylene from the feed mixture before it enters the main SMB adsorption system, thereby reducing the solvent requirements and improving overall process efficiency while maintaining high purity separation
2Productivity
If true moving bed (TMB) adsorptive separation is used, then counter current flow improves separation efficiency, but the filling material experiences friction and leakage making normal operation difficult
Solution Approach 1:
The patent segments the TMB system into multiple stationary adsorption columns that are operated in sequence rather than continuously moving the entire filling material. This segmentation allows the adsorbent to remain stationary in each column while simulated counter-current flow is achieved by sequentially switching between columns, thereby maintaining separation efficiency while eliminating friction and leakage issues
Solution Approach 2:
The patent creates a simulated version of the continuous counter-current flow by using discrete, stationary columns with periodic switching. The sequential operation of multiple columns replicates the effect of continuous counter-current flow without actually moving the filling material, thus achieving similar separation efficiency while maintaining operational stability
3Productivity
If conventional SMB process is used for p-xylene separation, then continuous separation is achieved, but low initial concentration of p-xylene in feed mixture limits productivity improvement
Solution Approach 1:
The patent applies preliminary action by introducing a pretreatment step before the main SMB separation process. The pretreatment column pre-concentrates p-xylene from the feed mixture before it enters the main SMB adsorption system, thereby reducing the solvent requirements and improving overall process efficiency while maintaining high purity separation
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 process significantly increases the productivity of p-xylene separation by raising the concentration of p-xylene in the feed, resulting in improved converted yield while maintaining product purity, as demonstrated by a 50% increase in p-xylene concentration and enhanced overall process efficiency.
Implementation Method 1
a separation process employing simulated moving bed (SMB) adsorptive chromatography
Implementation Method 2
contacting the fluid mixture with a solid adsorbent in the adsorption chamber and desorbing it with a desorbent
Data Source
AI summary
Provided is a process for adsorptive separation of p-xylene from an aromatic hydrocarbon mixture comprising other isomers of xylene, and a device used therein. More specifically, the present invention provides a separation process employing simulated moving bed (SMB) adsorptive chromatography, characterized by pretreating a fluid mixture, i.e. the feed, by using single adsorption chamber so as to raise the concentration of a component to be separated, and then carrying out the simulated moving bed adsorptive separation, thereby improving productivity, and a device used therein.