Two-Stage Sintering of Eco-Friendly Chromium-Free Bricks from Available Wastes

Abstract: Micronized refractory MgAl2O4-spinel as chromium-free bricks was prepared by powder-mixing defined amounts of aluminium and magnesium-hydroxides in two firing stages (900-1400 °C and 1600 °C). These hydroxides are chemically precipitated from Al-dross and dolomite aggregate wastes, respectively. The prepared spinel showed a high refractory quality. On firing under load up to 1500 °C, it linearly expanded by 0.7 %, with the beginning of subsidence occurring above 1500 °C. Also the sample had a nominal creep rate of subsidence (0.3 %/h). Generally, the dense spinel body prepared by mixing recycled powders at 1600 °C/2 h after pre-calcination at 1200 °C can be recommended for different applications at or above a service temperature of 1600 °C.