Illustration

A slag with high value of  is desirable for efficient desulphurization. Consider two different slags whose partition coefficient is 80 and 500. Amount of slag injected is , , and 12 kg/ton. To illustrate the role of transitory and permanent contact on desulphurization ,let use calculate for each case: The following table gives the calculated values

kg/ton  trans.  perm.  trans..  perm. 4 0.73 0.14 0.14 0.33 8 0.53 0.018 0.018 0.20 12 0.38 0.0025 0.0025 0.14

We note the following: 

• Both amount of slag and partition coefficient are important for desulphurization
  
  
• At lower  amount of slag and lower partition coefficient there is not much difference in the ratio of   for both permanent and transitory contact modes.. For example for  , when the powder injection rate is 4 kg/ton, the said ratio is 0.73 for transitory and 0.76 for permanent contact. However, when the powder injection rate is increased to 8 and 12 kg/ton, transitory contact mode becomes more efficient than permanent contact.  
  
  
• At higher value of , transitory contact gives much lower value of sulphur in metal than permanent contact

Transitory contact mode requires designing powder injection systems which can inject powder at constant and uniform rate.