What is the most widely used dechlorination agent in a conventional chlorine gas plant?

The most widely used dechlorination agent in a conventional chlorine gas plant is sulfur dioxide. Sulfur dioxide is effective in neutralizing residual chlorine in treated wastewater, thereby minimizing the harmful effects that chlorine can have on aquatic life if released into the environment. It reacts with chlorine to form chloride ions, which are not harmful, hence facilitating the dechlorination process and ensuring compliance with environmental regulations.

In contrast, while chlorine dioxide and hydrogen peroxide can also serve as dechlorination agents, they are less commonly used in standard practices at conventional chlorine gas plants. Chlorine dioxide is typically used more in disinfection applications rather than in the primary dechlorination of chlorine gas. Hydrogen peroxide does indeed help in dechlorination but is less favored due to its cost and handling considerations compared to sulfur dioxide. Hydrochloric acid is primarily utilized for pH adjustment and does not serve as a dechlorination agent. Therefore, sulfur dioxide stands out as the preferred choice in conventional settings for its cost-effectiveness and efficacy.