Radial-Flow Pyrolysis for Hollow Fiber CMS Membranes
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Solution Overview
Problem
Conventional pyrolysis techniques for carbon molecular sieve (CMS) membranes result in non-homogeneous fiber properties due to reactive off-gases reacting with pyrolyzing fibers, leading to inconsistent gas separation performance.
Innovation Solution
A method involving a pyrolysis chamber where pyrolysis gas flows perpendicular to the length of the membrane cartridge or bundle, either radially outward or inward, to minimize residence time and reduce detrimental reactions, using a porous center tube and sweep gas to enhance off-gas removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional axial pyrolysis gas flow is used, then heating and cooling objectives are achieved, but non-homogeneous off-gas concentration along membrane length causes non-uniform fiber properties
Solution Approach 1:
The patent inverts the conventional axial flow direction by implementing radial flow of pyrolysis gas perpendicular to the membrane length. This inversion causes off-gases to be swept away laterally rather than accumulating along the axial direction, resulting in more uniform off-gas concentration distribution and homogeneous fiber properties throughout the membrane.
Solution Approach 2:
The patent transitions from one-dimensional axial flow to two-dimensional radial flow by directing pyrolysis gas perpendicular to the membrane length. This dimensional change allows off-gases to be removed through a lateral pathway, preventing axial concentration gradients and achieving uniform fiber properties along the membrane length.
2Stability of the object's composition
If high pyrolysis gas flow rates are used to promote temperature homogeneity, then temperature uniformity is improved, but fiber entrainment and distortion occur
Solution Approach 1:
The patent changes the flow direction from axial to radial, creating a more distributed flow pattern that achieves temperature homogeneity through lateral heat transfer rather than requiring high axial flow rates. This dimensional change maintains fiber integrity while achieving thermal uniformity.
3Temperature
If pyrolysis gas flows axially through the membrane, then heat application is achieved, but reactive off-gases accumulate and react detrimentally with pyrolyzing fibers
Solution Approach 1:
The patent inverts the flow configuration by implementing radial flow perpendicular to the membrane length, causing pyrolysis gas to sweep off-gases away laterally rather than allowing axial accumulation. This inversion prevents harmful reactions between off-gases and pyrolyzing fibers while maintaining effective heat application.
Solution Approach 2:
The patent extracts off-gases from the pyrolysis zone by directing radial flow to sweep them away laterally through porous support structures. This extraction prevents off-gas accumulation and detrimental reactions while maintaining the necessary thermal environment for pyrolysis.
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 approach produces CMS membranes with more uniform properties and improved gas separation performance by reducing the impact of reactive off-gases, enhancing both permeance and selectivity across the membrane.
Implementation Method 1
A flow of pyrolysis gas is directed during said heating step past said cartridge or bundle in a direction perpendicular to the length direction of the cartridge or bundle, wherein performance of said heating step results in the production of pyrolysis off-gases and said flow of pyrolysis gas sweeps the pyrolysis off-gases away from the green, polymeric, hollow fiber membrane(s)
Implementation Method 2
The porous tube has at least one open end and apertures extending through a wall thickness of the porous tube
Implementation Method 3
Carbon molecular sieve membranes (CMS membranes) may be obtained by high-temperature pyrolysis under oxygen-deficient atmospheres of polymer precursors
Data Source
AI summary
One or more polymeric hollow fiber membranes are pyrolyzed to form one or more hollow fiber CMS membranes by directing a flow of pyrolysis gas through a polymeric membrane cartridge (including a porous center tube around which one or more green, polymeric, hollow fiber membranes is arranged) or a bundle of polymeric membranes (including a plurality of green, polymeric hollow fiber membranes oriented so that their ends are disposed with ends of the bundle) in a direction perpendicular to a length direction of the cartridge or bundle in order to sweep away off-gases that are formed during pyrolysis.