Refining of molten tin for removal of arsenic - by adding manganese alloy, which combines with arsenic to form foam which is sepd. from melt

摘要

Tin is melted and heated to 250-600, esp. 280-360 deg.C. A manganese cpd. is then added using a ratio of Mn:As in the tin of 0.5:1 to 2:1. The Mn cpd. reacts with the As to form a cpd. which is removed from the melt to leave pure tin. In the pref. process, a Mn alloy is pref. added using a ratio Mn:As of 05-0.9:1 with sepn. of the Mn-As cpd., and then adding a second batch of the Mn alloy using a ratio Mn:As of 1.3-2:1, followed by further removal of the Mn-As cpd. obtd. The molten Sn is pref. covered by a carbonaceous material, esp. wood chips or coal; or a gas, esp. N2, may be blown through the melt after adding the Mn alloy. The amt. of tin lost in removing the As is reduced, and toxic arsine is not formed by the metal foam contg. the Mn and the As.