Spent Magnesia-Carbon Refractory Bricks from Steel Production: Potentiality of MgO-Clinker Recovery

The work is focused on the quality of spent refractory materials (MC 98/10) from the slag line of steel ladles, which are freely dumped and the effect of their dumping in a landfill on the environment. The degradability of the spent refractories in water is an indicator of their corrosion extent. The stability of corrosion products was evaluated by batch leaching test in water and weak acid medium (pH = 5.95 and 4.21; liquid: solid =10). The conductivity and changes of pH in the medium were measured Crushed new magnesia-carbon bricks increase the pH value of leachates to 9 - 9.5, the spent refractory from the core of the bricks generates pH = 10 - 10.5 and that of the material from the corroded surface of bricks shifts pH up to 12. The alkali ions (Na+, K+, Ca2+) are eluted from the spent refractories. The increase of pH value to 11-12 leads to the saturation of solution with Ca2+, Al3+ and sulphur ions, and to the stabilisation of heavy metals in the solid compounds. Because the MgO-clinker particles concentrate in the coarse-grained fraction the re-use of size fraction > 1 mm from spent MC 98/10 bricks as raw materials is hopeful. The recycling processes are being verified and economic analysis is being prepared.