How to use sulfur dioxide to remove free chlorine from dechlorinated brackish water
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How to remove free chlorine from dechlorinated brackish water using sulfur dioxide? I heard that paper mills have free chlorine resulting from the use of sulfur dioxide for bleaching, but the specific process is not clear. I would like to ask everyone: what factors need to be taken into consideration when using sulfur dioxide to remove free chlorine from demineralized brine, and how can this be achieved? Could the amount of sulfur dioxide gas dissolved in the brine exceed what is necessary?
In an alkaline environment, sulfur dioxide has strong reducing properties and can reduce free chlorine in saline water. Based on the ORP analyzer for demineralized brine after dechlorination, it is possible to detect whether sulfur dioxide levels are excessive.
Can this be done by adding NaOH first, before introducing sulfur dioxide gas, in order to adjust the pH of the dechlorinated saline solution to 9-11? Then, sulfur oxide gas is added to the saline solution through a gas-liquid mixer; an ORP meter is installed on the pipeline for monitoring, and the amount of sulfur oxide gas added is controlled proportionally to keep the free chlorine at zero.