Metal recovery system from soots produced by the gasification process for heavy oil residue

Noncatalytic partially combustive gasification to carbon monoxide is one of an attractive process for the utilization of a heavy petroleum residue. Th e gasification operates in a reducing atmosphere, so a carbonaceous deposit (soot) containing iron, vanadium and nickel is produced. The extractive re covery of vanadium and nickel by nitric acid, sulfuric acid and a mixture o f sulfuric acid/ammonium sulfate aqueous solution from the soot obtained fr om a commercial process was carried out to elucidate the effects of extract ion conditions on the recovery rate of metals. Although 80% of vanadium was recovered from the soot collected from the gasification plant without pret reatment, the extraction ratio of nickel was below 20%. The dissolution rat e of nickel sulfide, which is the main component in soots, is slower than t hat of nickel oxide. To improve the recovery rate of nickel, the soot was p artially oxidized in air. The extraction ratio of nickel from the 90% oxidi zed soot rose to about 80%. A basic flow sheet for the metal recovery was proposed for a commercial pla nt based on the extraction results obtained.