The main results of calcination, and the consequent advantages in smelting are, for iron ores:

(1) Driving off water and thus avoiding interference with the regularity of the smelter fire.

(2) Elimination of Co2 and a consequent saving of fuel in smelting as the Co2 takes up much carbon from the fuel in the upper part of the blast furnace. This changes the carbonate ores to oxides.

Fig. 15. - Bridge crane for handling ore. The unloading hoists on the left take ore from vessels lying under them and pass it to the bridge crane in transfer cars. This crane carries it to its proper pile, according to composition, and also carries ore to the charging cars of the furnaces on the right.

(3) Elimination of sulphur in some ores, thus preventing its combination with the metal as it melts and runs down to the hearth of the furnace.

There is no advantage in calcining the magnetites and red hematites unless they contain pyrites. Ore deposits of the world which can be sent direct to the smelter without sorting or calcination are yet fairly abundant.

Fig. 15 shows the ore yard of a large smelting plant where ore is received for smelting.