Reactivity assessment of charcoal for use in silicon production

As charcoal is used in the silicon metal process, reactivity towards SiO is one of the most important properties that has strong effects on silicon recovery. The purpose of this study was to analyze anatomical properties of wood and charcoal, define a procedure to express the SiO reactivity in a simpler and more cost-efficient manner and indicate one or more clones of Eucalyptus with the greatest potential for production of charcoal to silicon use. Three hybrid clones of Eucalyptus urophylla × Eucalyptus grandis were used for the study and the coke was investigated for comparison purposes. Morphological analysis of fiber and vessels was carried out in wood, and the fiber wall area was determined on charcoal. The number of reactivity was calculated in five different protocols, based on the SiO reactivity test. To classify the charcoal with the greatest potential for silicon use, the parameter Readily Available Fixed Carbon Stock was created, based on charcoal`s most important properties. All charcoals had significantly higher SiO-reactivity than coke. In addition, an increasing trend of charcoal SiO-reactivity was found with decreasing wood basic density, apparent density and fiber wall area of charcoal, which are connected to porosity. All the reductant materials presented similar readily available fixed carbon stock. The developed procedure used for SiO reactivity measurements was a useful tool to classify charcoal for use in the silicon production process.