Formation of hexavalent chromium by reaction between slag and magnesite-chrome refractory

The goal of this work was to understand how Cr(6+) formation is affected by the interaction between chromite phases present in magnesite-chrome refractory and different slag compositions. In addition, the formation of Cr(6+) as a function of chromite particle Size and cooling rate due to the chromite phase/slag interaction was investigated. The following slag compositions were studied: calcium aluminate, calcium aluminum silicate, and calcium silicate. It was found that the presence of uncombined CaO in the calcium aluminate slags is responsible for a higher yield of Cr(6+). However, the replacement of Al(2)O(3) by SiO(2) in calcium aluminate slags decreases the formation of Cr(6+). SiO(2) reacts with CaO to form stable 2CaO . Al(2)O(3) . SiO(2) and CaO . SiO(2) phases, consequently decreasing the amount of uncombined CaO available to react with the chromite phase to form Cr(6+). Moreover, the content of Cr(6+), decreased by increasing chromite particle size and increasing the cooling rate of magnesite-chrome refractory.