Retrofitting Finite-Gap Electrolysis Cells to Zero-Gap
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Solution Overview
Problem
The 'finite-gap' design in membrane electrolysis cells leads to increased cell voltage due to ohmic drop, resulting in higher energy consumption and economic inefficiencies, necessitating a conversion to 'zero-gap' technology without complete replacement of existing cells.
Innovation Solution
A method involving plastic deformation of the rigid cathode to accommodate a pre-shaped conductive elastic element and a flexible catalytic-coated cathode, allowing for conversion to 'zero-gap' design without material waste, and reusing the cathode as a current collector, while maintaining even current distribution and reducing voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a finite-gap design is used with a rigid cathode spaced 1-3mm from the membrane, then the cell structure is simple and easy to manufacture, but the cell voltage increases due to ohmic drop resulting in higher energy consumption
Solution Approach 1:
The rigid cathode is plastically deformed to create a curved surface that follows the membrane contour, transforming the static finite-gap structure into a dynamic zero-gap configuration. This allows the cathode to adapt to membrane position variations while maintaining intimate contact, thereby eliminating ohmic losses without requiring complex adjustable mechanisms
Solution Approach 2:
The invention changes the geometric parameter of the cathode from a flat planar surface to a curved surface with specific radius of curvature. This parameter change enables the cathode to conform to the membrane surface, reducing the gap distance from 1-3mm to near-zero and consequently reducing the ohmic drop and energy consumption
2Use of energy by moving object
If a complete replacement of finite-gap cells with zero-gap technology is implemented, then energy consumption is reduced, but the cost increases due to complete removal and replacement of existing cells
Solution Approach 1:
The method performs preliminary plastic deformation of the rigid cathode within the existing cell structure to prepare it for zero-gap operation. This preliminary action allows the existing cathode to be adapted for new functionality without complete removal, thereby reducing conversion costs while achieving energy savings
Solution Approach 2:
Instead of discarding the existing rigid cathode during conversion, the invention recovers and reuses it by plastically deforming it into the appropriate curved shape. This recovery approach eliminates the need to purchase and install new cathodes, significantly reducing the economic cost of technology conversion
3Reliability
If plastic deformation is applied to the rigid cathode to achieve zero-gap contact, then current distribution becomes more even and voltages are minimized, but the manufacturing process becomes more complex
Solution Approach 1:
The plastic deformation process is segmented into localized zones between cathodic supports rather than requiring global cathode reshaping. This segmentation allows the deformation to be confined to specific regions, simplifying the manufacturing process while still achieving the necessary curvature for even current distribution across the membrane surface
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 method effectively converts 'finite-gap' cells to 'zero-gap' cells, minimizing energy consumption and avoiding the need for new current collectors, with demonstrated energy savings of about 150 kWh per tonne of caustic soda during chlor-alkali electrolysis.
Implementation Method 1
shaping of said rigid cathode by plastic deformation of the regions comprised between the contact surfaces with said cathodic supports
Implementation Method 2
overlaying onto said rigid cathode of a pre-shaped conductive elastic element having compressed regions in correspondence with the contact surfaces of said cathodic supports with said cathode
Implementation Method 3
an anodic compartment separated by an ion-exchange membrane
Implementation Method 4
the cell voltage to be penalised by a component associated with the ohmic drop generated by the current transport in the liquid phase between the cathode and the membrane
Implementation Method 5
overlaying of a flexible planar cathode provided with a catalytic coating onto said conductive elastic element
Implementation Method 6
electrolysis of alkali brines, in particular of sodium chloride brine aimed at the production of chlorine, caustic soda and hydrogen
Data Source
AI summary
The present invention concerns a method of retrofitting of a membrane electrolysis cell, wherein a rigid cathode is shaped by plastic deformation of the regions in correspondence of cathodic supports; a pre-shaped conductive elastic element having compressed regions in correspondence of said cathodic supports is overlaid onto said rigid cathode;a flexible planar cathode provided with a catalytic coating is overlaid onto said conductive elastic element. The invention also concerns a correspondingly retrofitted electrolysis cell.