P₂O₅ Solubility of Dephosphorization Slag in Citric Acid

GRAPHICAL ABSTRACT

Abstract

The dephosphorization slag produced by the duplex steelmaking process is suited for making steel slag phosphate fertilizer. The factors influencing P₂O₅ solubility of dephosphorization slag in citric acid were studied and a series of CaO-SiO₂-Fe_tO-P₂O₅ quaternary slag samples were prepared and analyzed. It was demonstrated that the corresponding P₂O₅ solubility varies from 81.6% to 97.9%. The P₂O₅ solubility increases with the increase of CaO/SiO₂, CaO/P₂O₅, CaO/(SiO₂+P₂O₅) and SCA (Surplus Calcium Alkalinity), and decreases with the increase of both Fe_tO and P₂O₅ content. Halide content has a notable negative effect on solubility in citric acid. The P₂O₅ solubility decreases from 92.5% to 47.1% with 1.0% CaF₂ added. When the content of CaF₂ reaches 6.0%, the solubility of slag is only 13.7%. With 2.0% and 5.0% CaCl₂ added, the P₂O₅ solubility decreases from 92.5% to 81.9% and 79.8%, respectively. In order to get a higher soluble slag, fluorine-containing and chlorine-containing substances cannot be added into the steelmaking converter. The addition of MgO and MnO has a positive influence on the P₂O₅ solubility in citric acid. The addition of Al₂O₃ shows an opposite influence. Na₂O can significantly improve the P₂O₅ solubility in citric acid solution.

Keywords:

• P₂O₅ solubility
• dephosphorization slag
• phosphate fertilizer
• citric acid