This column is based on “Chlorine Production from Sodium Chloride — Cost Analysis,” a report by Intratec. It can be found at: www.intratec.us/analysis/chlorine-production-cost.
Chlorine is among the most important chemical commodities — it is used in the manufacture of a multitude of end products (for example, plastics, solvents, pesticides, pharmaceuticals, disinfection chemicals and others), as well as in processes that produce industrial chemicals via organochlorine intermediates, such as polycarbonates, silicones, polyurethanes and others.
The following describes chlorine production by the electrolysis of aqueous sodium chloride (brine) using a conventional membrane process (Figure 1).
Figure 1. The above diagram shows chlorine production by the electrolysis of aqueous sodium chloride via a conventional membrane process[/caption]
Brine purification. Initially, recycled, depleted brine is mixed with water and re-saturated with fresh sodium chloride. Since other metal ions (such as Ca2+ and Mg2+) present in the brine would harm the membranes, the brine is treated with precipitants, so that the metals precipitate. The precipitated solids form a sludge, which is removed by settling in a clarifier. Subsequently,…