a method and apparatus for feeding alloy additive and burden materials to the burden in a vertical shaft furnace working volume generally by gravity - feeding the alloy additive to the furnace tuyere for entrainment in the blast media and transfer to the burden , which improves the recovery rate of the charged additive components in the molten metal and , allows utilization of undersized materials without secondary handling and treatment of the feed materials or utilization of pneumatic feed apparatus .