Refining dross is the result of lead refining process where impurities like copper, tellurium, arsenic-antimony-tin, silver, zinc and bismuth in sequence from lead bullion. Composition of each type of dross varies and is subjected to specific refining steps and raw material contents. Conversely, lead refining process are taken in account for the convenience of refining dross recovery.

Generally speaking, the copper dross is treated by reveberatory furnace. In case of copper dross with high arsenic, tin and antimony, caustic soda plus iron filings are used. In reaction with caustic soda, the arsenic, tin and antimony report to sodium salt as slag to be recovered by hydrometallurgy consequently. After soda refining, the copper matte is treated by cupellation method to separate copper with lead, and lead reports into slag phase. Complete separation of Te, As, Sn and Sb is accomplished by chemical methods in a leaching plant.

Apart from conventional dross treatment methods, Metalcess focuses on treating tin slag from Harris refining process, silver-zinc crust/silver foam from Parkes process and lead anode slime treatment. With Metalcess solution, high purity tin is obtained by combining fire-refining and vacuum distillation.

Metalcess provides an integrated system combining liquation and distillation technology to treat silver-zinc crust/silver foam from Parkes process, in which zinc, lead and silver are separated efficiently at the cost of low energy consumption. Noticeably, the zinc recovered from silver-zinc crust can be used as desilvering agent again for the Parkes process. While the lead alloy can be charged to lead refining pot before bismuth-removing step. This system is superior in reducing energy consumption, shortening process flow and improving working environment.