Hydraulic recycling of green sands.

Context

The regeneration of chemically bonded sands is well mastered. But this is not true of naturally clay-bonded sands: they cost more and more to dispose of and no recycling approaches have been developed (especially for small volumes). Can a hydraulic technique be used to recycle these sands in new sand for core making? Can the clay and the carbon present in these sands be recovered and fed back into the circuit ? Is the technique profitable?

Cleaned grains of sand.

Work done

Survey of the market out to 2010: tonnage of green sand discharged in France.
Search of the literature for ways to treat green sands.
Laboratory study of various hydraulic treatment methods.
Technical and economic assessment.

	Résults
	A hydraulic treatment process combining attrition, classification, magnetic separation and centrifugal sludging, in a preliminary feasibility study, allows the following levels of re-use of this waste in the foundry: - 65% of the used green sand can be recycled for core making (mixed with new sand) - 6% active bentonite and seacoal can be recycled for moulding (half the incoming fraction). The operation is profitable for installations from 5 t/h up. The results will be confirmed on a prototype.