Investigação da formação e efeitos do clorato sobre a reação de desprendimento de hidrogênio no processo de cloro-soda com tecnologia de diafragma

Abstract

In this work, the formation and effects of chlorate ion were studied over hydrogen evolution reaction (HER), focusing for the chlorine and alkalis production by diaphragm process, using a pilot and bench cells, respectively. Studies in pilot cell revealed that chlorate formation is dependent of NaOH concentration in liquor and brine dwelling time. It was also observed that the NaOH concentration increase in the cathodic side provoked decreasing of diaphragm structure lifetime. This phenomenon reduced the blockage efficiency to back migration and consequently, increasing NaOH concentration in the anodic chamber, further increase in the undesirable parallels reaction rate, for example, the chlorate formation. After formation of chlorate in the anodic chamber the migration to the cathodic side is inevitable. Therefore to complete the studies we decided to verify the influence the chlorate, in bench cell, in the cathodic side, specifically for HER process. Potential polarization experiments in presence of chlorate, evidenced effects of HER wave displacement over SAE1020 mild steel carbon steel plate employed in industrial cells for chlorine and alkalis production using diaphragm process. Alternatively to SAE1020, other duplex alloys like SAF2205, SAF2304 and SAF2507 were also investigated. SAF2205 alloy presented a very interesting electrocatalytic response for HER. Pilot cell results pointed for the problem detected with the NaOH migration to the anodic side of cell, and invoked the single possibility to solve this problem - the changing of diaphragm cell separator. Bench experiments revealed chlorate influence on HER over SAE1020 carbon steel, claiming for urgent developing of alternative materials/cathodes with chlorate-immune character.