A Study of Ammonia Reaction Behavior During the Calcination of NH4VO3 in the Vanadium Metallurgy Process and Its Potential Application

In the current study, non-isothermal kinetics of NH4VO3 calcination were investigated under an air atmosphere and argon atmosphere, and the produced gas was detected by TG-MS. The results showed that the calcination process of NH4VO3 under an air atmosphere could be divided into three stages, corresponding, respectively, to the three-step deamination stage of NH4VO3 (α = 0.00–0.69; α = 0.69–0.93; α = 0.93–1.00). Furthermore, the calcination of NH4VO3 under an argon atmosphere could roughly be divided into five stages: α = 0.00–0.03; α = 0.03–0.50; α = 0.50–0.69; α = 0.69–0.94; and α = 0.94–1.00. The release of ammonia gas (NH3) in NH4VO3 could be divided into three stages regardless of the specific atmosphere, and the corresponding mechanisms were all the diffusion reaction. The activation energies for all the calcination stages were all less than 100 KJ/mol. However, a distinct stage (α = 0.94–1.00) of self-decomposition ammonia reduction of high-valent vanadium oxides emerged under the argon atmosphere. The activation energy at α = 0.95 for the reduction of high-valent vanadium oxides by self-decomposed ammonia to low-valent vanadium oxides was 53.0 KJ/mol. The sealed system could effectively promote the progress of the ammonia reduction reaction as shown in the fifth stage (α = 0.94–1.00), thereby achieving the full utilization of self-decomposed ammonia and the green preparation of different kinds of low-valent vanadium oxides during the vanadium metallurgy process.