This is one of two Barrel Furnaces (the East furnace can be seen in the back) where the blister copper is further refined into anode copper ready for casting, it is here that the oxygen and sulfur content is adjusted. These furnaces also receive scrap material thru the large doors seen on top and from a small shaft furnace used to recycle used anodes. The round "barrel" shape of the furnace allows it to be rolled in one direction so the last remaining process slag content can be poured off leaving nothing but 99.99% pure copper in the bath after which it is rolled in the opposite direction to pour off the copper for casting.