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Mind the Gap

Posted On : Friday 14th June 2019

When it comes to efficiently and cost effectively producing chlorine, caustic soda or hydrogen using electrolysis, the membrane process is becoming the preferred method based on reduced energy consumption, lower investment costs and reduced environmental risk.

Designing a membrane cell involves delivering a consistent voltage across the electrolyte. This is best achieved by minimising the gap between the electrodes, however, when the gap is very small, gas bubbles can be created between the electrodes and the membrane leading to an imbalance of voltage within the cell.

To create a more uniform distribution of the operating voltage, excellent results are achieved by filling the gap between the cathode and the current distributor with an elastic element such as knitted nickel wire mesh.

The knitted wire mesh is strong, flexible and resilient created from interlocking wire loops that offer a resiliency or “springiness” to the knitted mesh. The knitted mesh is heat and corrosion resistant making it ideal for applications in electrochemistry and fuel cells where harsh environmental conditions preclude the use of other materials.

The knitted mesh can be produced from a range of materials including metals, synthetics and ceramics. Mesh can also be created from different diameter wires, in different densities and stitch patterns, using different knitting structures and forming techniques. The mesh type can be tailored to suit the individual requirements or operating environment.

The design of the elastic element of knitted mesh plays a fundamental role in the operation of a zero-gap membrane cell. It is composed from a complex array of nickel wires, profiled in a precise shape to create the required elastic response needed for a good electrical contact.

Construction characteristics are tailored to fit different available gaps, aiming to deliver a constant mechanical pressure onto the membrane with no damage to its mechanical integrity. The elastic properties of the mesh are selected in order to optimise both electrical contact and good resistance to pressure fluctuations or reverse pressure.

The mesh also acts as a pressure equalizer, is easily compressed and has high resiliency providing ‘spring-like’ elastic memory and response. The ‘spring like’ nature of the mesh also ensures that the cell clamping pressure is distributed uniformly and offers consistent firmness over a specific area, creating effective electrical contact over the entire electrode surface whilst minimising local areas of too high or too low pressure.

Its open structure provides easy access of the electrolyte to the electrode and ready escape of the electrode product, whether gas or liquid. There is little or no resistance to gas or electrolyte flow through the compressed collector.

This flexibility means that it’s well suited for a range of applications including; electro-chemistry, fuel cells, power to gas alkaline electrolyser cells, between layers in fuel cell stacks or modular fuel cell cartridge or stacks.

For further information on knitted mesh and its wide variety of applications, please contact a member of the team on info@knitmesh.com or get in touch through our social media pages.