Comminution of permanent lining material of asbestos cement to be used in the cement industry mixed with waste oil

About 30 million tons of sheets and other products of asbestos cement had been produced in Germany until its use was prohibited by law in 1991. An amount of > 500 000 t/a of demolition waste of asbestos cement should be expected in the next few years. The Recycling and Waste Act gives priority to retrieving material from waste or to use them energetically rather than dumping. There am some methods aiming at a complete destruction of the asbestos fibre structure of the extremely noxious asbestos cement products and at a utilization of the after-products. One of these methods is a process developed by IBU-tec GmbH Weimar providing to feed an asbestos cement fuel mir into the flame of the burning zone of the rotary kiln of a cement plant completely converting the fibre morphology of asbestos and absorbing all modified residual materials as clinker constituents. Prerequisite for this thermal process is the comminution of the asbestos cement lining material and the preparation of a free-flowing mix consisting of the precrushed asbestos cement and waste oil, as investigated in this case. Technological examinations were carried out concerning the primary crushing of permanent lining material of asbestos cement (sheets) with regard to a suitable particle size, as feed of a ball mill, as well as concerning the subsequent grinding of asbestos cement waste oil mixtures in the mill. It turned out that asbestos cement has a very poor grindability due to the fibre inclusions consequently resulting in a high power demand. Proposals are made how to design a large-scale plant with a throughput of 5 t/h to produce a fine-grained mix of asbestos cement and waste oil.