GB365945A - Improvements in the recovery of sulphuric acid from the acid sludge of oil refineries - Google Patents

Abstract

Ammonium sulphate; calcium phosphates.--Sulphuric acid is recovered from acid sludge obtained in the refining of petroleum &c. by treating the sludge with an aqueous sulphuric acid solution of ammonium sulphate in such an amount that the ammonia content of the resultant mixture is at least 0,8 mols. per mol. of sulphuric acid whereby the carbonaceous and resinous materials in the sludge are caused to coagulate and are separated. Preferably 0,8-1,2 mols. of ammonia per mol. of sulphuric acid is used, the operating temperature being such that all the ammonium sulphate or <PICT:0365945/III/1> bisulphate formed remains in solution. The resulting sulphuric acid ammonium sulphate liquor may be used to treat rock phosphate preferably after its acid content has been increased by the addition of strong sulphuric acid. The resulting superphosphate may be neutralized by the addition of liquid ammonia to obtain a fertilizer. Anhydrous liquid ammonia is sprayed from a nozzle 2 and sulphuric acid or sulphuric acid ammonium sulphate liquor obtained in the process is sprayed from a lower nozzle 6 into a packed tower 1. The resulting aqueous sulphuric acid solution of ammonium sulphate passes continuously to a mixing vessel 8 to which acid sludge is also supplied continuously by way of conduit 9. The vessel 8 is provided with cooling coils 11. The liquid overflows from the mixing vessel through a conduit 10 into a settling tank 5 where resinous and carbonaceous material is removed by skimming. A portion of the residual solution is returned by a pump 7 and conduits 4 to the spray 6 of the tower 1. The sulphuric acid ammonium sulphate liquor not thus recirculated is withdrawn through a conduit 13. If the packing in the tower 1 becomes clogged it may be flushed with water from a conduit 14.ALSO:Sulphuric acid is recovered from acid sludge obtained in the refining of petroleum &c. by treating the sludge with an aqueous sulphuric acid solution of ammonium sulphate in such an amount that the ammonia content of the resultant mixture is at least 0,8 mol. per mol. of sulphuric acid whereby the carbonaceous and resinous materials in the sludge are caused to coagulate and are separated. Preferably 0,8-1,2 mols. of ammonia per mol. of sulphuric acid is used, the operating temperature being such that all the ammonium sulphate or bisulphate formed remains in solution. The resulting sulphuric acid ammonium sulphate liquor may be used to treat rock phosphate preferably after its acid content has been increased by the addition of strong sulphuric acid. The resulting superphosphate may be neutralized by the addition of liquid ammonia to obtain a fertilizer.