EXPERIMENTAL RESEARCH ON RECOVERY OF METALS FROM STEEL DUST

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Evaporation roasting for steel dust, in which roasting detrimental non-ferrous elements is separated from iron, has been carried out. We have investigated evaporation of following elements ; zinc, lead, tin, copper, sodium, potassium and chlorine. We intend the non-ferrous elements and the iron to be used as resource in their extraction process. The experimental results are summarized as follows :(1) When we roast steel dust with CaCl_2 under oxidized condition over 1300K,copper well evaporates as copper chloride. Carbon containing in steel dust makes reduced condition and lead to lowers copper evaporation efficiency, the carbon must hence be oxidized prior to the roasting. Lead evaporates more easily than copper does in the roasting. Twenty percent of zinc in the dust evaporates as chloride gas under oxidized condition.(2) The evaporation of tin proceeds with mixing CaCl_2 under reduced condition over 1300K.Thereby 90% of tin in the dust is removable in the best condition.(3) Zinc evaporates under reduced condition without CaCl_2 addition.(4) Sodium and potassium evaporate well both in oxidized and reduced condition. Vapor spices of the elements is not identified.Iron content in the residue of the evaporation roasting, that depends on dust, is 40 to 60%, which is comparable with iron making resource but too low to use that in steel making. The residue is crashed, and then iron is collected by magnetic separation. Iron thus enriches up to 80% and recovery of iron in the magnetic separation is 90%. It is theoretically possible to separate the detrimental elements from iron and to use them in their extraction process but the roasting and separation processes are rather complicated and need a cost.