| 摘要 |
<p>Scale and rust are removed from iron and steel by pickling in an aqueous sulphuric acid solution which is replenished to keep the acid concentration between 8% and 20% by weight of sulphuric acid, heated to between 140 DEG F. and 180 DEG F., preferably by steam jets, and agitated by the discharge of compressed air. Ferrous sulphate is allowed to build up in the solution until Fe is between 8% and 12% of it by weight, then the solution is transferred to a crystallizer and cooled to below 140 DEG F. and preferably below 80 DEG F., so that the ferrous sulphate crystallizes as ferrous sulphate heptahydrate. When the solution has been freed of the crystals so formed it is replenished with fresh acid and returned to the pickling bath. Vapours from the pickling bath may be collected and acid recovered from them and returned to the bath.ALSO:Ferrous sulphate is allowed to build up in an aqueous sulphuric acid solution in which iron and stell are pickled until Fe is between 8% and 12% of it by weight, then the solution is transferred to a crystallizer and cooled to below 140 DEG F., and preferably below 80 DEG F., so that the ferrous sulphate crystallizes as ferrous sulphate heptahydrate. When the solution has been freed of the crystals so formed it is replenished and returned to the pickling bath. Vapours from the pickling bath may be collected and acid recovered from them and returned to the bath, which is replenished to keep the acid concentration between 8% and 20% by weight of sulphuric acid and is heated to between 140 DEG and 180 DEG F., preferably by steam jets, and is agitated by discharge of compressed air.</p> |
