Enormous stocks of ore, limestone, and coke must be ever ready for charging into the insatiable stack; this means great piles of ore and stone, and plenty of coke either being made or continuously coming into the plant. Reliable and powerful bridges, cranes, grab buckets, transfer and scale cars, etc., must be in place to span the stock piles and to load the skips.
Huge stoves are built in line near the furnace to heat the blast; four stoves, each nearly as big around and as tall as the furnace itself, are commonly supplied to heat the blast. The stoves are thick steel shells with firebrick linings and checkerwork fillings. Through one hot unit the blast always will be passing on its way from the engines to the furnace, while the others will be heating ready to take their turn at half-hour intervals.
Fig. 19. Exterior View of Part of s Blast-Furnace Plant.
In a building near the furnaces powerful engines will be at work compressing the air to go to the furnaces. These engines may be steam driven by means of boilers heated with the furnace gas; they may be gas engines driven by the furnace gas burned internally; they may be turbine engines driven by steam from gas-heated boilers. In any case, the power plant is a very important part of the plant.
Fig. 19 indicates clearly enough the furnace sticking up through its casting room on the right of the picture. The gas is led from the top of the furnace through the downcomers and dust collectors across to the line of stoves and the boiler house (both in center of the picture). The power plant is the larger building on the left and behind this is the water tower for the plant supply. At the very left edge is the location of the casting machinery; the hot pig iron has to be switched over to this building in the big ladles before it is cast into pigs.
The molten iron is tapped out of the furnace and runs into ladles to go to either the steel plant or the casting machine. In the steel plant the iron probably will be poured into a large receiver and from there will be taken, still molten, to the steel furnaces. Iron to be used in trade or stored for future use is cast in molds which are strung together, conveyor fashion, so as to give continuous service. These ingots of iron, or pigs as they are called, fall from the casting conveyor on to flat cars for storage or transportation. An older method of casting was to run the metal out into closely packed sand molds; it is little used today. For further handling of the pigs, cranes with an electromagnet for tackle are employed.