The recovery of vanadium from ash obtained during the combustion of fuel oil at thermal power stations

Abstract

The recovery modes of vanadium from the vanadium-containing ashes of foreign thermal power stations (the Fiomo Santo station (Italy) (sample 1) and stations in Leina, Germany, (sample 2) and Cagliari, Italy (sample 3)) are established. It is shown that there is no single approach to directly recovering vanadium from various ashes. Each ash needs its own leaching mode depending on its chemical and phase compositions, namely, for samples 1 and 2, this is leaching with water and 9% sulfuric acid at S: L = 1: 4 and t = 60–80°C for 30 min; for sample 3, this is leaching with 5% sulfuric acid in the presence of hydrogen peroxide at S: L = 1: 4 and t = 20°C for 30 min and then for 60 min at 60°C. The conditions for the hydrolytic precipitation of vanadium from the leaching solutions are selected. It is shown that, in order to isolate it from solutions at the stage of hydrolytic precipitation most completely, it is necessary to change the degree of oxidation of vanadium to +5 using hydrogen pentoxide at t = 20°C for 30 min and then precipitate vanadium peroxide at pH = 1.8–2.0 and t = 95°C for 2 h.