| 摘要 |
The solution of composition: Sulphate of: A1 (expressed as Al2O3)...6.88 % Fe (expressed as Fe2O3)...0.195 % Na (expressed as Na2O)....1.5 % Ti (expressed as TiO2)....0.113 % K (expressed as K2O).....1 % H2SO4 uncombined............29.7 % at 120 DEG C, is brought to 78 DEG C by evaporation under vacuum, leading to the departure of 55 g of water per 1000 g of initial solution. The solution is introduced at 78 DEG C at a charge of 1056 l/h continuously into a first crystalliser maintained at 70 DEG C. A suspension of Al2(SO4)3.0.5 H2SO4.11 to 12 H2O is formed. This suspension is passed successively into three other crystallisers in which it is maintained, each time, for three hours at 60 DEG C, 50 DEG C and 40 DEG C. At the outlet of the fourth crystalliser, the suspension is filtered and a cake is recovered comprising crystals of composition Al2(SO4)3.0.5 H2SO4.11.5 to 12 H2O having very low contents of impurities. |
