Method for manufacturing briquettes containing a calcium-magnesium compound and an iron-based compound, and briquettes thus obtained

Method for manufacturing a calcium-magnesium composition in the form of fired briquettes, comprising the following steps:

• i. supplying a homogeneous pulverulent mixture comprising at least one quick calcium-magnesium compound, said mixture comprising at least 40 wt % of CaO+MgO equivalent relative to the weight of said composition and having a Ca/Mg molar ratio greater than or equal to 1,
• ii. feeding a roller press with said homogeneous pulverulent mixture, said roller press being equipped with rollers provided with pockets,
• iii. compressing said homogeneous pulverulent mixture in said roller press, while obtaining a calcium-magnesium composition in the form of green briquettes, and
• iv. collecting said green briquettes,
• said method being characterized in that said homogeneous pulverulent mixture further comprises an iron-based compound present at a content of at least 20 wt % of Fe2O3 equivalent relative to the weight of said composition, said iron-based compound having a granulometric distribution characterized by a median size d50 below 100 μm as well as a size d90 below 200 μm, in that said “quick” calcium-magnesium compound is burned dolomite, said burned dolomite having a value of t70 below 10 min, in that the rollers of the roller press develop linear speeds at the periphery of the rollers between 10 and 100 cm/s and linear pressures between 60 and 160 kN/cm, and in that the method further comprises a thermal treatment of said collected green briquettes at a temperature between 900° C. and 1200° C. for a predetermined duration of between 3 and 20 minutes, while obtaining fired briquettes containing calcium ferrite and having simultaneously a Shatter Test Index less than 8%, and a porosity value greater than or equal to 30%.