Carbonatation de la chaux dans les réfractaires dolomitiques - influence des stabilisants sur la réactivité de l'oxyde de calcium avant et après passage dans l'industrie sidérurgique

Magnesium is one of the strategic resources for EU industry as mentioned in their last reports. Defined as the lightest metal, magnesium is highly considered in the transport industry to limit CO2 emissions and its consideration for Strategic Technologies and Sectors of EU increases continuously (Robotics, UAV, 3D printing or digital technologies). China is currently the main Mg supplier with 91% worldwide and 97% in EU. To reduce dependence on China, a few projects were devoted to sustainable European magnesium production. Freedom project, consisting of the production of Mg metal based on dolomitic refractory waste recycling, is one of them. This project is divided into two parts: first, the extraction of pure MgO from the refractory waste and secondly, the reduction of MgO in Mg metal. Dolomitic refractory is composed of MgO and CaO phases that must be separated for the MgO recovery. Bicarbonate process is a 40’s American process studied for MgO production from dolomite Mg.Ca(CO3)2. This process, modernized to consider the current energy and climate considerations, is composed of 5 reaction steps. This work will be achieved on the first reaction, lime carbonation to stabilize the calcium under its carbonate form CaCO3 in front of its hydroxide form Ca(OH)2. Dolomitic refractories are sensitive to moisture because of the CaO presence and must be stabilized to preserve their mechanical properties. Iron and silica are slaking inhibitors added to the material to create calcium ferrite and/or calcium silicate. However total stabilization reduces corrosion resistance to basic slags and semi-stabilized dolomitic refractories are often faced in the industry. This research topic will allow us to understand the impact of those inhibitors on carbonation reaction and the influence of steel industry on those refractories.