[STANSFIELD & harrison] THE REDUCTION OF IRON ORES 



177 



contains 22.27 per cent, of oxygen, while the corresponding vertical 

 line is located at about 24 per cent, of oxygen. The positions of these 

 vertical lines vary somewhat with the temperature and probably 

 depend on the mutual solubility of the compounds, thus the first 

 vertical line may correspond with Fe304 with Fe203 dissolved in it. 

 The final inclined part of the curve, when less than 4 per cent, of 

 oxygen remains, indicates metallic iron with dissolved FeO; all the 

 free FeO having disappeared. 



100 



80 



S 60 



o 

 8 ^0 





— ^-^^ 



y 3 



30 26 22 IS 14 10 6 2 



Per Cent O In Solid Phase 



Fig. 2. Equilibrium for the Reduction of Fe203 by CO at 863°C.— Matsubara. 



The present research was directed to finding the rate of reduction 

 rather than the equilibrium conditions, but some approximate 

 measurements of equilibrium, indicated by the dotted line in Fig. 1, 

 were made to show how closely the CO2 in the issuing gas corresponded 

 with the equilibrium proportion. 



The volume of carbon monoxide passed per hour was 1500 c.c. 

 in the earlier experiments, but twice and even four times that speed 

 was employed in some of the later tests. 



In Fig. 3 are collected the curves showing the rate of reduction 

 of hematite and magnetite at various temperatures in a stream of 

 3000 c.c. per hour of carbon monoxide, this stream being sufBciently 

 fast to maintain a decided excess of carbon monoxide throughout 

 the reduction. It will be seen that at 800° hematite is almost per- 

 fectly reduced in an hour and a half, while magnetite is only 55 per 

 cent, reduced in that time at 850° and requires three hours for an 

 80 per cent, reduction at 850° or 900°C, Speaking generally, it 

 appears that hematite ores can be reduced effectively by carbon 

 monoxide at temperatures of 750° or 800°C., while magnetite ores 

 need temperatures of from 850° to 900°C., and even at these tempera- 

 tures the reduction is far slower. 



12— c 



