Process and equipment for reprocessing moist foundry sand

摘要

In a process for reprocessing moist foundry sand, which is moved in a closed circulation, the used sand is classified in at least two process steps, a transverse-flow air classification into a coarse fraction and fine fraction taking place in each case in the second and every further stage, while either a mechanical separation or likewise a transverse-flow classification is carried out in the first stage and the excess sand arising in the second or last stage is in each case added to the fines separated off. Equipment suitable for carrying out the process operates either only as a multi-stage transverse-flow classification with the same separation limit in each stage or as a combined mechanical or transverse-flow classification, either a part of the used sand in the lastmentioned case or a part of the fines arising in the mechanical separation being passed via the transverse-flow classification. In this way, it is possible in particular to remove even non-magnetic metal impurities effectively from the used sand and to increase the fines fraction in the reprocessed used sand or to lower the separation limit.