GB670085A - Improvements in circulatory systems for the regeneration of spent solutions from thepickling of ferrous metals - Google Patents

Abstract

<PICT:0670085/III/1> In a process involving the crystallization and recovery of iron sulphate heptahydrate from the used pickle liquor for ferrous metals and the re-use of the mother liquor, concentrated sulphuric acid is added to the used liquor during agitation thereof, and the regenerated liquor from a previous crystallization step is passed through a conduit in the used liquors so as to absorb the heat produced by the addition of the acid and to bring the regenerated liquor substantially to pickling temperature. The amount of acid used is such as to obtain an acid concentration of 125-200 g./litre for a concentration of iron ranging from 125 to 105 g./litre as sulphate, the acid concentration being higher as the sulphate concentration is lower. In Fig. 1, the liquor from pickling tanks B is pumped to tank 10 provided with a stirrer 29 to which 60 DEG B<\>ae sulphuric acid is added from tank 12. The heat produced is removed by passing regenerated liquor from tank 22 through coil 14, whence it passes via pipe 24 to regenerated liquor tank 18 or to the first of the pickling tanks. The solution then passes to tank 32 provided with stirrer 29 wherein it is cooled by the passage of water through coil 35, the water passing to outlet cock 36a or via cock 37a to regenerated liquor tank 18. The liquor now containing suspended ferrous sulphate heptahydrate passes to settling tank 16 from which the mother liquor is decanted at 17 into tank 18 whence it is pumped to tank 22. A drain plug 30 is provided in the settling tank. If desired, tank 10 only may be employed, in which case after the acid addition, first the solution from tank 22, then water through pipe 39, is passed through coil 14, the water escaping through pipe 40. Another Figure is provided illustrating the use of single heat exchange tank. Conversely, any desired number of such tanks may be employed. The Specification as open to inspection under Sect. 91, discloses the use of a centrifugal filter in place of a settling tank. This subject-matter does not appear in the Specification as accepted.