Studies on the use of two different magnesia-carbon recyclates as secondary raw material for MgO-C refractories

Two magnesia-carbon (MgO-C) recyclates were investigated with respect to their utilization as raw materials for MgO-C refractories. X-ray diffraction and backscattered electron diffraction were used for phase analysis of the recyclate aggregates. In addition, the gas released from one of the recyclates when it came into contact with water was analyzed in a mass spectrometer. MgO-C samples with different recyclate contents were produced. During coking, the samples showed different behavior depending on the recyclate used. Whereas those con-taining the first recyclate showed a slight shrinkage, a significant increase in volume was observed in the case of the specimens that contained the second recyclate. The volume increase could be reduced by thermal pre-treatment of this recyclate at 380 degrees C. As a result, better bulk density and porosity values were obtained. However, an even stronger positive effect was achieved by replacing the pitch-based binder used in the binder system with a novolak-based.