Propylene Oxide Membrane Purification with Particle Pre-Filtration
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Solution Overview
Problem
Existing membrane separation processes for removing poly(propylene oxide) from propylene oxide are prone to fouling and clogging due to the presence of large particles, leading to operational inefficiencies and potential catalysis of additional poly(propylene oxide formation, especially when the feed has high concentrations.
Innovation Solution
A two-step process involving a filtration screen with openings up to 50 μm followed by a membrane with pore sizes of 0 to 30 nm is used to purify propylene oxide, where the filtration screen removes large particles and the membrane achieves high rejection of poly(propylene oxide), minimizing fouling and ensuring high purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a membrane with small pore size (0 to 5 nm) is used to remove poly(propylene oxide), then poly(propylene oxide) rejection is improved, but membrane fouling and clogging by large particles increases
Solution Approach 1:
The filtration process is divided into two distinct stages: first a coarse filtration screen (5 μm) removes large particles, then a fine membrane (0 to 5 nm) removes poly(propylene oxide). This segmentation allows each stage to be optimized for its specific function without compromise.
Solution Approach 2:
The coarse filtration screen performs preliminary removal of large particles before the feed reaches the membrane. This preliminary action prevents the membrane from being exposed to fouling particles in the first place.
2Reliability
If a filtration screen with larger openings is used, then membrane fouling is reduced, but poly(propylene oxide) removal efficiency decreases
Solution Approach 1:
The system uses a two-stage filtration approach where a coarse screen (5 μm) handles particle removal and a fine membrane (0 to 5 nm) handles poly(propylene oxide) rejection. This segmentation allows optimal pore sizes for each stage without compromise.
Solution Approach 2:
The coarse filtration screen acts as an intermediary between the feed and the membrane, removing large particles that would otherwise cause fouling, while allowing the membrane to focus on its primary function of poly(propylene oxide) rejection.
3Ease of operation
If membrane cleaning and replacement frequency is reduced, then operational robustness is improved, but poly(propylene oxide) concentration may increase
Solution Approach 1:
The coarse filtration screen performs preliminary removal of fouling particles before they can reach the membrane. This preliminary protection action significantly extends membrane life and reduces cleaning frequency while maintaining consistent poly(propylene oxide) rejection.
Solution Approach 2:
The system provides beforehand protection to the membrane by using the coarse filtration screen as a sacrificial element that absorbs the fouling impact, cushioning the membrane from direct exposure to particles that would cause fouling.
4Device complexity
If a single membrane separation step is used, then device complexity is reduced, but reliability due to fouling and clogging decreases
Solution Approach 1:
The filtration system is segmented into two functional units: a coarse filtration screen and a fine membrane. This segmentation distributes the fouling burden and allows each component to be optimized for its specific pore size range.
Solution Approach 2:
The system uses two different porous materials with different pore sizes: a coarse porous screen (5 μm) for particle removal and a fine porous membrane (0 to 5 nm) for poly(propylene oxide) rejection. This multi-scale porous structure addresses both fouling prevention and contaminant removal.
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 effectively reduces poly(propylene oxide) concentration to below 1 ppm, enhancing process flexibility and operational robustness, and produces propylene oxide suitable for both slabstock and moulded polyurethane foams without frequent membrane cleaning or replacement.
Implementation Method 1
a) sending a stream comprising propylene oxide and poly(propylene oxide) to a filtration screen having openings with an average diameter of at most 50 μm
Implementation Method 2
b) sending the filtrate stream resulting from step a) to a membrane having an average pore size of from 0 to 30 nm and recovering a permeate stream from the membrane as a purified propylene oxide stream
Data Source
AI summary
The invention relates to a process for removing 5poly(propylene oxide) from propylene oxide, comprising: a) sending a stream comprising propylene oxide and poly(propylene oxide) to a filtration screen having openings with an average diameter of at most 50 μm; and b) sending the filtrate stream resulting from step a) to a membrane 10 having an average pore size of from 0 to 30 nm and recovering a permeate stream from the membrane as a purified propylene oxide stream.