Partially Coated Gas Separation Membrane for Selectivity and Flow
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Solution Overview
Problem
Existing gas separation membrane systems face a trade-off between selectivity and product flow rate, with fully coated membranes improving recovery but reducing flow, and uncoated membranes increasing flow but reducing recovery, while also experiencing higher pressure drops.
Innovation Solution
A partially coated gas separation membrane module where hollow fibers are coated along approximately three-quarters of their length, with the permeate gas exiting opposite to the main feed stream due to a baffle, allowing for improved selectivity and product flow while minimizing pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the entire lengths of the membrane fibers are coated with surfactant solution, then the selectivity for separating air into oxygen and nitrogen is improved, but the permeability of the membrane is reduced and the product flow rate is reduced
Solution Approach 1:
The membrane fiber is divided into two distinct segments: a coated segment and an uncoated segment. The coating is applied only to a portion of the fiber length rather than the entire length, creating spatial segmentation of functional properties along the fiber axis
Solution Approach 2:
Different regions of the membrane fiber are given different properties: the coated region provides enhanced selectivity for gas separation, while the uncoated region maintains high permeability and lower pressure drop. This local differentiation of quality allows simultaneous optimization of both selectivity and flow characteristics
2Productivity
If an uncoated module is used, then the product flow is improved, but the product recovery is reduced and the pressure drop along the length of the fiber is higher
Solution Approach 1:
The fiber is segmented into coated and uncoated regions, where the coated segment recovers permeate gas effectively (improving product recovery) while the uncoated segment allows high flow with low pressure drop
Solution Approach 2:
The uncoated region locally provides low resistance to flow (maintaining high product flow and low pressure drop), while the coated region locally provides enhanced separation performance (improving product recovery)
3Manufacturing precision
If a coated membrane is used, then the selectivity is improved, but the pressure drop along the length of the module is higher
Solution Approach 1:
The membrane fiber is segmented into coated and uncoated portions along its length, allowing the system to benefit from both coated (high selectivity) and uncoated (low pressure drop) regions
Solution Approach 2:
The coating is applied locally to specific regions where selectivity enhancement is most beneficial, while leaving other regions uncoated to maintain low flow resistance and minimize pressure drop across the module
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 partially coated module achieves 10-25% more product flow and 10% improved recovery compared to prior art, while reducing pressure drop by 35%, effectively combining the benefits of both coated and uncoated modules.
Implementation Method 1
A polymer used in air separation, for example, will pass oxygen and nitrogen at different rates. The gas that preferentially flows through the membrane wall is called the 'permeate' gas
Implementation Method 2
U.S. Pat. No. 5,141,530, the disclosure of which is incorporated by reference herein, describes a solution, in water, of a non-ionic surfactant which, when applied to the membrane, improves its selectivity for the separation of air into oxygen and nitrogen
Implementation Method 3
Gas permeates through the membrane due to the pressure differential between one side of the membrane and the other
Data Source
AI summary
A gas separation module includes fibers formed of a membrane which exhibits selectivity between gaseous components to be separated. The fibers are partially coated with a solution which enhances their selectivity, the fibers being uncoated in the vicinity of their feed ends. The partially coated fibers provide a good compromise between the goals of improved selectivity and enhanced product flow. The gaseous component that permeates through the membrane is made to flow in a direction opposite that of the main gas feed, due to a baffle that directs the permeate in the desired direction. The invention also includes a method and apparatus for making the partially coated module.