VAKUUMFILTRATION VON ALPHA-HALBHYDRAT AUS HALBHYDRAT-H TIEF 3 PO TIEF 4 -PROZESSEN

摘要

Process comprises passing alpha-CaSO4 hemihydrate (I) suspension from a reactor to a continuously-operating vacuum filter and filtering at a temp. is not >20, esp. is not >10 degrees C below the hemihydrate-dihydrate transition temp. while filtering an absolute pressure of 400-600 mm Hg is maintained on the vacuum side of the filteR. Esp. a horizontal vacuum-band filter is used and (I) is also washed and pre-dried in the filter. In the filter the mother liquor is removed in the first zone, then the solids washed with water in a second and pressed dry in a third. Under these temp. and pressure conditions hardening of the filter cake and fouling of the filter by encrustation are avoided.