Processing used foundry sand for re-use - by parallel wet-processing to remove inorganic binders heating to remove organic binders, then mixing two separate prods.

摘要

Processing used foundry sand (I) contg. mainly inorganic binders, esp. bentonite (''used inorganic sand'') (II) and organic binders, esp. phenolic and/or furan resins (''used organic sand'') (III) comprises collecting the (II) and (III) separately, wet processing the (II) and heat treating the (III) (opt. after crushing in each case), and at least partly mixing the two types. After wet procsesing, (II) contains 12-18 wt.% water or is dehydrated to this level before mixing, is wet processed with or without attrition. Final temp. of (III) after heat treatment is 700-1000 deg.C. After mixing, the end prod. is subjected to pneumatic treatment, and is pref. classified into at least 2 fractions which are bunkered separately. Corresp. amts. of these fractions are then measured out (opt. with new sand) to produce foundry sand of the required mean grain size or in a given band of grain sizes. USE/ADVANTAGE - The invention provides a relatively simple and economical process (w.r.t. prior art processes) for processing used foundry sand so that most of the harmful residues are removed and the prod. can be reused.