Luisa María Cabalin
Full professor at the University of Malaga
An Analytical Technique for the Sorting of Waste Refractory Materials Used in Steelmaking Industries.
Refractories are indispensable for all high temperatures processes, such as the production of metals, cement, glass and ceramics. Over a great many years, spent refractories recycling received little attention due to the abundance of low cost virgin raw materials and low disposal costs of the largely inert materials. However, during the last years, interest in recycling spent refractories increased, due to the fact that many high quality raw materials are becoming increasingly difficult to obtain and prices are rising. Furthermore, the reuse of recycled refractories has become more attractive because of the potential benefits both from an economic (cheaper raw materials, lower treatment costs, reducing costs for landfilling) and environmental (saving virgin resources, reducing wastes and lower energy demand and CO2 emissions compared to virgin materials) point of view. This is why technological innovations in recycling plants for refractory wastes as raw materials for the production of new refractories are focused on automating the sorting process according to the type of refractory.
Laser Induced Breakdown spectroscopy (LIBS) is a spectrochemical analytical technique using light emitted by micro-plasmas created by short laser pulses on the sample surface. This rapid chemical analysis technology offers many compelling advantages that are really necessary for the analysis of this type of sample, including:
– A sample preparation-free measurement experience
– Broad elemental coverage
– Versatile sampling protocols that include fast raster of the sample surface and depth profiling
The crucial factor that determines the realistic operation of LIBS in order to properly sort spent refractories is the complex spectral similarity revealed by the refractory products, which usually contain Al2O3, MgO and SiO2 in varying proportions. This is why LIBS has been combined with chemometrics in order to deal with the large number of complex analytical data generated. An efficient algorithm has been implemented to classify with great accuracy refractory residues coming from different characteristic zones of a steel ladle according to their emission spectral information.
The figure 1 shows the LIBS sensor developed at the University of Malaga, during the analysis of a refractory sample
Figure1. Sensor LIBS designed and developed at the University of Malaga