Caustic soda production
The chlorine-soda process is an electrochemical process that enables production by electrolysis of chlorine gas, caustic soda and hydrogen, starting from a sodium chloride solution (brine). Production of chlorine and soda can take place using diaphragm cells, membrane cells or mercury cells.
Costacurta’s wire cloths are used in the chlorine-soda process with diaphragm cells.
During this process, in order to prevent the chlorine that develops at the anode from coming into contact with the catholyte, the anodic compartment is kept separate from the cathodic compartment by an ion-permeable diaphragm that is impermeable to Cl2 molecules. This diaphragm, which was once made of asbestos, is now normally made of fluorinated polymer fibres (PTFE).
The sodium chloride solution (anolyte) is introduced into the anode compartment and flows into the cathode compartment, under a hydraulic head.
In the first compartment, the CI ions are oxidised to produce chlorine gas. In the second compartment hydrogen and sodium hydroxide is produced (NaOH caustic soda).
The cathode groups of diaphragm cells (bottom grids and “cathode fingers”) are made with a special wire cloth in carbon steel, produced by Costacurta.
To ensure that the layer of fibres that forms the diaphragm can be deposited evenly over the cloth, it is important that its surfaces are relatively flat and even, and that its thickness is constant and controlled.
Costacurta makes a high-quality calendered wire cloth for caustic soda production, with a flat surface and controlled thickness, and is able to supply custom-made flat panels or shaped and welded individual elements (cathode fingers), according to the client’s technical specifications and construction drawings.