Dephosphorization requires oxidizing and basic slag:

(9)

(10)

(11)

•   in slag should be high. This means slag should have free dissolved lime.
  High basicity of slag is required.
• in slag should be high; slag should be oxidizing. However for efficient
  dephosphorization the FeO content of slag should be in between 15 to 16%.

• Low temperature favours high

Conditions for simultaneous removal of C and P

Removal of C and P both require oxidizing conditions but P removal is possible only when a basic and limy slag is formed. Consider the following reactions occurring simultaneously

(12)

(13)

(14)

(15)

It is assumed in eq. 14 and 15 that henrian activity is equal to (wt %). Both reactions 12 and 13 require oxygen but reaction 13 requires a slag which is basic in nature in addition to oxygen. Thus, if carbon and phosphorus are to be removed simulataneously, an important requirement is the availability of slag which acts as a sink for (). Thermodynamically slag is required in which activity coefficient of   is very low. The question is how low activity of  should be?. This value can be determined by equations 14 and 15 Replacing [wt% O] in equation 14 and 15, and after rearrangement,