Preparation of special silicon steel grade MgO from hydromagnesite

Abstract A preparation technology of MgO powder used in special silicon steel from hydromagnesite mineral has been developed. The preparation technology includes the following steps: (1) calcining the hydromagnesite at 700–750°C for 1.5–2 h; (2) hydrating the calcined hydromagnesite to be slurry containing the solid-liquid ratio of 15–20 g·L −1 ; (3) acquiring Mg(HCO 3 ) 2 solution by carbonating the slurry, the carbonation temperature, CO 2 pressure, and end point PH value of carbonation are less than 40°C, 0.4–0.6 MPa, and 7 respectively during the carbonation process; (4) preparing precipitated basic magnesium carbonate by thermally decomposing the Mg(HCO 3 ) 2 solution at 90–100°C; (5) obtaining the MgO product by calcining the precipitated basic magnesium carbonate at 850–950°C for 30–60 min, and adopting flowing nitrogen during the cooling process. By using this technology, more than 80wt% magnesium in hydromagnesite mineral can be extracted, and high-performance MgO products used in special silicon steel can be obtained.