Hydrogen Membrane Permeate Overpressure Design
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Solution Overview
Problem
Existing methods for separating hydrogen from hydrogen-containing gas mixtures in submarines, such as those using methanol reformers, face challenges with high-pressure hydrogen-permeable membranes that require thick walls for stability, leading to reduced permeability and costly materials, and suffer from thermal expansion issues causing membrane detachment and contamination.
Innovation Solution
A method involving a hydrogen-permeable membrane subjected to flushing gas overpressure on the permeate side, using a non-hydrogen flushing gas like steam, which maintains high purity hydrogen separation while allowing for thin-walled membranes, and a device with a flushing gas circuit for recycling and separation, ensuring mechanical stress reduction and efficient hydrogen recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick-walled membrane is used to withstand high reformate pressure, then mechanical stability is improved, but permeability decreases and cost increases
Solution Approach 1:
The patent inverts the conventional pressure approach by applying higher pressure on the permeate side rather than the feed side. This reverse pressure application allows the use of thin-walled membranes while maintaining structural integrity, as the pressure gradient is reversed to work in favor of the thin membrane design rather than against it.
Solution Approach 2:
The patent changes the pressure parameter distribution across the membrane by applying sweeping gas pressure on the permeate side that exceeds the feed side pressure. This parameter inversion enables thin-walled membranes to function effectively, combining high permeability with sufficient mechanical stability through controlled pressure differential.
2Productivity
If a thin-walled membrane with ceramic support structure is used, then permeability is improved, but thermal expansion differences cause membrane detachment and contamination
Solution Approach 1:
The patent extracts and eliminates the ceramic support structure from the membrane assembly. By using thin-walled membranes without rigid ceramic supports, the source of thermal expansion mismatch is removed entirely, preventing membrane detachment and contamination while maintaining high permeability through the thin membrane design.
Solution Approach 2:
The patent introduces sweeping gas as an intermediary medium on the permeate side. This sweeping gas serves multiple functions: it prevents condensation of permeated hydrogen, maintains pressure differential, and eliminates the need for ceramic support structures that cause thermal expansion issues, thereby resolving the reliability problem.
3Productivity
If high reformate pressure is applied on the inlet side, then hydrogen separation efficiency is improved, but mechanical stress on the membrane increases
Solution Approach 1:
The patent inverts the conventional pressure application by applying higher pressure on the permeate side rather than the feed side. This reverse pressure strategy maintains the necessary pressure differential for efficient hydrogen separation while reducing mechanical stress on the membrane, as the pressure gradient is applied in the opposite direction to what would create excessive stress.
Solution Approach 2:
The patent uses sweeping gas as a substitute or copy of the conventional high-pressure feed approach. Instead of relying solely on high feed pressure to drive separation, the sweeping gas on the permeate side creates an equivalent driving force through pressure differential, achieving the same separation efficiency with reduced mechanical stress.
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 ensures high purity hydrogen separation with reduced mechanical stress on the membrane, enabling the use of thinner, less expensive membranes and complete hydrogen recovery, while preventing non-hydrogen gases from leaking through potential membrane damage points.
Implementation Method 1
a hydrogen-permeable membrane used for separating the hydrogen
Implementation Method 2
the water is converted from the vaporous to the liquid state by condensation
Data Source
AI summary
Separating hydrogen from a hydrogen-containing gas mixture, comprises separating hydrogen at a hydrogen permeable membrane (8) from the remaining gas mixture and applying a permeate side (20) of the membrane with a purging gas pressure, which is greater than or equal to the pressure of the gas mixture on the inlet side of the membrane. An independent claim is also included for a device (2) for separating hydrogen from the hydrogen-containing gas mixture comprising a membrane unit (6) comprising the hydrogen permeable membrane, where the membrane unit comprises a purging gas inlet (18) and a pressurized gas source on the permeate side of the membrane.