Reusing Hydrochloric Acid
The HCl electrolysis unit consists of two groups of electrolysers, each group having five electrolysers. The electrolyzers and rectifiers are electrically connected in series via busbars.
Each electrolyser consists of 36 elements. The decomposition of Hydrochloric Acid occurs at the anodes and cathodes, with these electrodes made of graphite and separated from each other by diaphragms. The individual graphite electrodes are mounted in frames made of a synthetic material resistant to Hydrochloric Acid and Chlorine.
Hydrochloric Acid at 34% is fed back to HCl electrolysis, producing Chlorine gas on the anode side and Hydrogen on the cathode side. As a result, Hydrochloric Acid is also recovered from the electrolysers at a lower mass concentration, typically 17%. This 17% Hydrochloric Acid, with no commercial value, is sent to the Hydrogen Chloride absorption unit where, together with demineralised water, it is used to absorb the Hydrogen Chloride and produce - again - Hydrochloric Acid with a mass concentration of 34%.
Bondalti receives Hydrogen Chloride through a pipeline, from a partner also located in the Estarreja industrial complex, which is a secondary product of the production process, and uses Chlorine gas produced and sent by pipeline by Bondalti.
This gas, once absorbed, is transformed into Hydrochloric Acid at 34%, and is once again fed to the HCl electrolysis, where Chlorine gas is produced and sent to the aforementioned partner, thus restarting the cycle.
The Hydrogen produced in the electrolysis is internally consumed in the Aniline production process.
