Abstract: On account of the shortcomings of high consumption of sulfuric acid for leaching, lime for neutralizing leaching solution and water during the process, as well as large emission of tailing, both laboratory and pilot experiment are conducted on returning and reuse of residual acid by adding to solution. Effect of the accumulation of V₂O₅ in leaching solution on leaching efficiency after residue acid returning in laboratory scale is investigated. Lime consumption for neutralization and the output of filter residual before and after neutralization on residual acid returning is compared. Pilot experiment is based on laboratory experiment. Appropriate fresh sulfuric acid and the returning acid are added into solution when V₂O₅ concentration is 8~18 g/L, only fresh acid is used when V₂O₅ concentration is above 18 g/L, and only returning acid when the V₂O₅ concentration is less than 8 g/L. By this method, consumption of sulfuric acid, lime and water during leaching-neutralization process are decreased by 22.1%, 16.3%, 71.4% respectively, also the residual solution output decreased by 15.3%, which indicates that the residual acid returning technology can significantly lower the consumption and emission.

Key words: Stone coal, Vanadium extraction by acidic leaching, Residual acid returning, Consumption and emission reduction