Field Museum of Natural History 



DEPARTMENT OF GEOLOGY 

 Chicago, 1922 



Leaflet Number 2 



Models of Blast Furnaces for 

 Smelting Iron 



Three models represent the hot blast furnace of 

 today, the cold blast furnace of seventy years ago and 

 the small forge in which iron was smelted one hundred 

 and fifty years ago. 



I. THE MODERN IRON BLAST FURNACE. 

 Practically all the iron in use is extracted from its ore 

 in blast furnaces, one of which is represented in mini- 

 ature by the model in the right half of the case. It is 

 called a blast furnace because its operation is main- 

 tained by a blast of air blown in from below. Its prod- 

 uct is pig or cast iron which, remelted and shaped in 

 molds, forms our cast iron objects. All steel and 

 wrought iron is refined from this pig iron. The process 

 of smelting iron ore is based on simple principles al- 

 though the practice of smelting is decidedly complex in 

 detail. A mixture of ore, limestone and fuel is fed in at 

 the top of a tall furnace (the furnace reproduced is 

 sixty-five feet high) . The fuel, coke prepared from soft 

 coal, is made to burn with great intensity by a blast 

 of hot air blown in from below. Hot gases formed by 

 the incomplete combustion of the coke attack the ore 

 which is a combination of iron and oxygen and take 

 away its oxygen. This leaves the iron behind in a 

 free state. Lower in the furnace this iron absorbs 

 carbon from contact with hot coke, melts and falls to 

 the hearth below whence it is drawn off from time to 

 time in molten condition. The earthy impurities of 

 the ore and the ash of the coal combine with the lime- 



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