Staged Membrane System for Gas Separation
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Solution Overview
Problem
Conventional multi-stage membrane systems for gas and vapor separations require high compressor power, increasing compression costs while aiming to maintain product recovery and purity, especially when using high selectivity and permeance membranes.
Innovation Solution
Implementing a multi-stage membrane system with a pre-membrane and secondary membrane made from high selectivity and permeance polybenzoxazole or cross-linked polybenzoxazole polymers, where the permeate from the pre-membrane is directly sent to either the waste or product stream, reducing the need for inter-stage compression and optimizing membrane area usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional multi-stage membrane systems compress permeate from the primary membrane before sending it to the secondary membrane, then product recovery and purity are improved, but compression cost and energy consumption increase significantly
Solution Approach 1:
The membrane system is divided into three distinct stages: a pre-membrane with high selectivity and permeance, a primary membrane, and a secondary membrane. The pre-membrane performs the critical function of selective separation without requiring compression, while the primary and secondary membranes handle bulk separation and final purification respectively. This segmentation allows the high-performance membrane to operate in a favorable pressure regime, eliminating the need for energy-intensive compression while maintaining high product recovery and purity.
Solution Approach 2:
The pre-membrane acts as an intermediary component between the feed stream and the primary membrane. It pre-concentrates the permeate components with high selectivity and permeance, creating a favorable feed composition for the subsequent primary and secondary membranes. This intermediary stage eliminates the need for compression by performing the selective separation function that would otherwise require mechanical compression, thereby reducing energy consumption while maintaining product quality.
2Reliability
If high selectivity and high permeance membranes are used throughout the entire multi-stage system, then product recovery and purity are maximized, but manufacturing cost increases significantly
Solution Approach 1:
Different membrane materials with appropriate properties are assigned to different stages of the system. The pre-membrane uses high-selectivity and high-permeance polybenzoxazole polymer to perform critical selective separation where it is most needed. The primary and secondary membranes use commercially available, lower-cost membranes with adequate separation performance for their respective functions. This local optimization of membrane quality matches performance requirements to functional needs, maximizing product recovery and purity while minimizing manufacturing costs.
Solution Approach 2:
The system changes the key parameter of membrane selectivity across different stages. The pre-membrane has very high selectivity (greater than 20, preferably greater than 30) to perform the critical pre-separation function. The primary and secondary membranes have lower, but sufficient, selectivity appropriate for their bulk separation and final purification roles. This parameter gradient allows the system to achieve high overall performance while using cost-effective membranes in the stages where high performance is less critical.
3Ease of manufacture
If the pre-membrane area and secondary membrane area are kept small to reduce cost, then manufacturing cost is reduced, but product recovery may be compromised
Solution Approach 1:
The pre-membrane is designed with very high permeance, which compensates for its small area. The high permeance parameter allows a compact pre-membrane to achieve the necessary separation capacity. The secondary membrane, also with small area, uses the high-selectivity polybenzoxazole polymer to achieve effective separation with minimal membrane area. This parameter optimization allows the system to maintain high product recovery while using smaller, more cost-effective membrane areas in the pre and secondary stages.
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 configuration reduces inter-stage compression costs, enhances product recovery and purity, and maintains cost-effectiveness by utilizing high-cost membranes only in specific stages, while maintaining high thermal stability and resistance to contaminants.
Implementation Method 1
a new type of high permeability polybenzoxazole polymer membrane for gas separations
Implementation Method 2
These polybenzoxazole polymer membranes exhibited extremely high CO2 permeability (>1000 Barrer) for CO2/CH4 separation
Data Source
AI summary
The present invention involves the use of a multi-stage membrane system for gas, vapor, and liquid separations. In this multi-stage membrane system, high selectivity and high permeance or at least high selectivity polybenzoxazole membranes or cross-linked polybenzoxazole membranes are applied for a pre-membrane or both the pre-membrane and the secondary membrane. A primary membrane can be from conventional glassy polymers. This multi-stage membrane system can reduce inter-stage compression cost, increase product recovery and product purity for gas, vapor, and liquid separations. It can also save the cost compared to the system using all the high cost polybenzoxazole membranes or cross-linked polybenzoxazole membranes.