Two-Stage Oxygen-Water Separation for PEM Electrolyser Loops
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Solution Overview
Problem
Existing methods for separating oxygen from water in PEM electrolysis systems are inefficient, particularly for small bubbles, leading to performance degradation and potential explosions due to explosive mixtures, and lack flexibility in system configuration.
Innovation Solution
A two-step separation process using a horizontal separator and a coalescer, with hydraulic decoupling between vessels, to rapidly remove oxygen from a heterogeneous mixture of gas and liquid, enhancing safety and adaptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional degassing tank is used to separate oxygen bubbles from water, then separation can be achieved, but the apparatus becomes large and expensive, and small bubbles cannot be separated effectively
Solution Approach 1:
The separation process is divided into two distinct stages: a first separation unit that removes large oxygen bubbles using gravity and a second separation unit that removes small bubbles using coalescing elements. This segmentation allows each unit to be compact while achieving complete separation, resolving the contradiction between separation effectiveness and apparatus size.
Solution Approach 2:
The second separation unit employs coalescing elements with porous structures that capture and merge small oxygen bubbles. These porous materials provide a large surface area within a compact volume, enabling effective separation of fine bubbles without increasing the overall apparatus size, thus resolving the contradiction between separation effectiveness and compactness.
2Device complexity
If oxygen bubbles are allowed to return to the electrolyser, then system complexity is reduced, but performance degrades and explosion risk increases
Solution Approach 1:
The invention extracts and removes oxygen bubbles from the water stream using a two-stage separation system. By completely removing oxygen before water returns to the electrolyser, the harmful effects of oxygen accumulation (performance degradation and explosion risk) are eliminated while maintaining relatively simple system architecture.
Solution Approach 2:
The invention converts the potentially harmful oxygen bubbles into a separable phase by using the density difference between gas and liquid. The oxygen bubbles, which would otherwise cause harm, are extracted and removed, transforming a harmful factor into a manageable separation process that protects system performance and safety.
3Temperature
If large amounts of water are circulated to limit temperature rise, then thermal management is improved, but oxygen accumulation increases leading to safety risks
Solution Approach 1:
The invention extracts oxygen bubbles from the circulating water stream at strategic points in the circulation loop. By removing oxygen during circulation rather than allowing it to accumulate, the system can maintain large water circulation for thermal management without incurring the safety risks of oxygen accumulation.
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 method achieves rapid and nearly complete separation of oxygen from water, improving system performance and safety by preventing explosions and allowing flexible system modifications.
Implementation Method 1
the oxygen bubbles require a certain amount of time, depending on their size and the flow direction of the water, to rise to the water surface due to the density difference
Implementation Method 2
a second separation step using a second separation unit
Data Source
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AI summary
A method of treating a heterogeneous mixture comprising a gas and a liquid is proposed, wherein the method comprises the steps of subjecting the heterogeneous mixture or a part thereof to a first separation step using a first separation unit (1) and thereafter to a second separation step using a second separation unit (2), producing a remainder depleted in the gas and comprising at least a part of the liquid of the heterogeneous mixture, passing the remainder or a part thereof to a pump feed reservoir (4), and pumping the remainder from the pump feed reservoir (4), wherein the first separation step removes a first part of the gas from the heterogeneous mixture and the second separation step removes a second part of the gas from the heterogeneous mixture. Corresponding apparatus (100, 200) is also proposed.