Utilization of Recycled Material for Producing Magnesia–Carbon Refractories

Abstract

The partial replacement of primary raw materials for the production of refractories with recycled ones gains in importance, as it contributes to the conservation of natural resources, energy saving, and reduction in greenhouse gas emissions. In this work, the use of a magnesia–carbon (MgO-C) recyclate in the fractions 3–6, 1–3, and 0–1 mm as a raw material for MgO-C refractories was investigated. The recyclate was examined via optical and scanning electron microscopy. Using mixtures with different recyclate contents up to 82 wt%, MgO-C specimens were prepared to study the influence of the recyclate on their chemical composition, structure, and properties. The substitution of primary raw materials with the recyclate did not cause a decrease in the MgO content analyzed after carbon burnout, but the contents of the individual impurities changed. A comparison of the MgO-C that contains 82 wt% recyclate with the recyclate-free material through computed tomography indicated a change in the size distribution of the MgO grains. The porosity increased, and the cold modulus of rupture decreased with increasing recyclate content, whereas the thermal shock resistance improved. At a recyclate content of 40 wt%, the refractoriness under load was only slightly lower than that of the recyclate-free material.