钒氧化物还原过程中物相转变热力学规律研究

Thermodynamics for Phase Transformation in the Reduction Process of Vanadium Oxides

针对钒氧化物间接还原条件下的逐级还原规律进行理论计算,其逐级还原规律为：当温度在273~987K时,V_2O_5→VO_2→V_3O_5→V_2O_3→VO→V;当温度在987~2 500 K时,V_2O_5→VO_2→V_2O_3→VO→V;分析了钒氧化物稳定存在的温度区间,分别为：VO_2为273~623 K,V_3O_5为623~713 K,V_2O_3为713~1 393 K,VO为1 393~1 882K,V为1 882~2 500 K;得到了V-O-CO系平衡状态图。同时考虑压力与活度对于平衡状态图的影响,获得了变化规律。增加C和S的含量能够降低钒的活度,增加Si、Mn、P、V、Ti、Cr的含量则会增加钒的活度,考虑钒的活度时氧化钒的初始还原温度变为1 213 K;压力的增加会使氧化钒还原的初始温度升高,压力分别为0.000 1、0.001、0.01、0.1、1 MPa下,初始还原温度分别为943、1 053、1 190、1 381、1 642 K。

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 V305 ,713 -1 393 K for V2O3,1 393-1 882 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 oxides,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.