Models of Blast Furnaces 5 



This coming- in contact with hot iron ore abstracts its 

 oxygen and frees the iron. This iron is set free in a 

 comparatively pure form which melts with difficulty. 

 Even in the intense heat of the hotter part of the fur- 

 nace it would only become pasty. In contact with the 

 hot coke each particle of iron absorbs a small quantity 

 of carbon which gives it the composition of cast iron 

 which melts readily at furnace temperatures. The 

 iron then melts and drops to the bottom of the fur- 

 nace where it collects in a molten slate in the cruci- 

 ble. When a sufficient quantity of iron has collected 

 it is withdrawn through the TAP HOLE. This is a 

 small round hole at the base of the furnace connect- 

 ing with a shallow groove or channel in the floor in 

 front. This tap hole is closed by a stopping of fire 

 clay or other refractory material. When the time 

 comes to tap the iron, the clay stopping is broken 

 out and the iron allowed to run into the channel which 

 may conduct it to a pig bed, not shown in the model, 

 where it is cast in sand molds and takes the form of 

 rough blocks called PIGS. When a steel works is 

 connected with the furnace plant, the molten iron as 

 tapped is conveyed directly to the mills for conver- 

 sion to steel. 



The blast furnace runs continuously and all that 

 enters must escape in a gaseous or liquid state as there 

 is no provision for removing solids. Earthy matters 

 not easily fusible are present in the ores and in the 

 ash of the fuel. Limestone from the furnace charge 

 combines with these and under the influence of heat 

 forms a fusible waste product, the SLAG or CINDER. 

 This floats on the molten iron in the crucible and runs 

 off through the SLAG EYE. This is a small opening 

 a little below the tuyeres and to the right which a man 

 with an iron rod is cleaning. The blast of air is pro- 

 vided by BLOWING ENGINES which do not appear 



[in 



