Supercritical fluid extraction of grinding and metal cutting waste contaminated with oils

The wellknown technique of supercritical fluid extraction with compressed carbon dioxide is used for an environmental application. The development of a process is described, in which residues with high oil contents from metal machining operations such as grinding or cutting can be separated in two fractions. One consists of the oil which can be recovered from the grinds in such a quality that direct reuse as grinding oil is possible; the metal fraction can be recycled by common processes. The results obtained in laboratory scale equipment were scaled up and successfully demonstrated in a pilot plant.