Original Date: 06/02/1997
Revision Date: 01/18/2007
Best Practice : Solid Chemical Additions
Sharretts implemented a method of solubilizing dry chemicals for its zinc-plating operations. Previously, technicians would analyze the bath chemistries of the plating tanks and add dry chemicals (e.g., potassium chloride, ammonium chloride, boric acid, potassium permanganate) directly to the tanks if they were beyond specified parameters. However, technicians usually had to add twice as much chemicals as the analysis indicated before the tanks were within parameters. Upon investigation, Sharretts discovered that 50% to 60% of the dry chemicals never solubilized. As a result, large amounts of sludge were accumulating inside the plating bath tanks. The sludge was frequently cleaned out of the tanks and disposed as hazardous waste.
To resolve the situation, Sharretts purchased vessels that had mixers. Technicians now add dry chemicals to the vessel along with either an aqueous or zinc solution. The mixer blends the chemicals and liquid into a slurry, which keeps the chemicals in a liquid state. The slurry mixture is then added to the plating bath tanks as needed, resulting in 90% to 95% solubility. Sharretts also uses rinse water to replenish the tanks as the heated process baths evaporate. This procedure produces higher-quality rinse water for the tanks and less-concentrated process rinse water for the waste stream.
Sharretts’ method of solubilizing dry chemicals for its zinc-plating operations has produced many benefits. By pre- mixing the dry chemicals, Sharretts has reduced chemical usage, minimized sludge disposal, and decreased the frequency of operational shutdowns for cleaning the plating tanks.
For more information see the
Point of Contact for this survey.