Method for preparing a foundry sand mixture

A method for recovering moulding sand from a foundry sand mixture, which comprises at least one proportion of moulding material fragments or loose moulding material grains, which accumulates when a cast part is demoulded from a casting mould as a result of destruction of casting cores or moulded parts representing the cast part which have been formed from the moulding sand and an inorganic binder and optionally one or a plurality of additives to set properties of the moulding material, wherein the method comprises the work steps:

• a) mixing the foundry sand mixture with cleaning water to form a slurry, in order to dissolve inorganic binder residues contained in the foundry sand mixture and optionally present additives from the moulding sand and to rinse them out of the foundry sand mixture, and
• b) separating the cleaning water contaminated with the inorganic binder residues from the moulding sand contained in the slurry,
• characterised in that a process temperature of the slurry formed from the cleaning water and the foundry sand mixture (work step a)) is 80 to 200° C. and the slurry is mixed for a dwell time of 5-60 minutes, and
• the contaminated cleaning water accumulating in work step b) is reused at least once for work step a).