Thermodynamics for Phase Transformation in the Reduction Process of Vanadium Oxides

The rule of step-by-step indirect reduction of vanadium oxides was calculated theoretically.It is concluded that the indirect reduction of vanadium oxides follows the rule of V₂O₅→VO₂→V₃O₅→V₂O₃→VO→V at 273~987 K while V₂O₅→VO₂→V₂O₃→VO→V at 987~2 500 K.The temperature intervals for steady existence of vanadium oxides are 273~623 K for VO₂,623~713 K for V₃O₅,713~1 393 K forV₂O₃,1 393-1 882 K for VO and 1 882~2 500 K for V,respectively.The equilibrium diagram of V-O-CO system was obtained, and the effects of pressure and activity on the equilibrium diagram were investigated.The activity of vanadium,decreases with increase in C and S content but increases with increasing the content of Si,Mn,P,V,Ti and Cr, and the initial reduction temperature of vanadium oxides turns into 1 213 K considering the influence of activity of vanadium.The initial reduction temperature of vanadium ox-ides,rising with increase of system gas pressure,reaches to 943 K,1 053 K,1 190 K,1 381 K and 1 642 K as gas pressure is 0.000 1 MPa,0.001 MPa,0.01 MPa,0.1 MPa and 1 MPa,respectively.