In a process for treating composite elements of solid organic and/or inorganic composite materials-such as composites of metal/metal, plastic/plastic, metal/plastic or mineral composites with metals and/or plastic materials-solid particles are produced from the composite elements and they are added to a transport fluid, wherein at least one flow obstacle which crosses the flow of the mixture of solid particles and transport fluid is moved relative to said flow as a flow-breakaway edge for forming eddies which acceleratingly break up the mixture. The mixture is fed to the separation or break-up procedure at the flow-breakaway edge or edges with an acceleration of 20 to 25 m/sec.sup.2 and the composite element is preferably crushed prior to the separation or break-up procedure.