Circular economy as applied to refractory materials

Abstract

The closed-loop economy concerning refractory materials is implemented through systematic involvement in post-operational usage in thermal, including metallurgical, units as secondary (by-product) raw materials. This is one of today's trends in resource and energy economics, reducing carbon footprint and CO2 emissions, decreasing waste with subsequent disposal in landfills. Purified scrap of refractory materials is used as supplementary materials in metallurgical processes, commonly referred to as scrap utilization when used as fluxes to adjust slag composition in metallurgical units, molded materials for welding in converters, refractory fillers in the production of unformed materi-als for sections lining working outside the aggressive influence of molten metal and slag, etc. For these purposes, the scrap is sorted into grades, crushed and screened, occasionally incorporating other products. Refractory scrap after ser-vice in metallurgical units usually has higher impurity content, higher porosity, and contains fragmented remnants of the refractory structure. Recycling refractory scrap may additionally involve technological methods for extracting impurities (enrichment) with subsequent use of the recyclate directly in refractory production, partially replacing primary raw materials. In this case, research work with involvement of qualified specialists and the entire body of knowledge in creating new refractory materials is necessary. Practice has shown that qualified involvement of recyclate in manufacturing processes of high-quality refractories is accompanied by solving non-standard tasks and requires a special approach, including the issue of removing introduced or formed foreign materials in refractory material during its operation. Enrichment is an effective direction for cleaning refractory scrap, extracting quality materials during processing of waste from mining enterprises, materials of technogenic origin to obtain recyclate of necessary quality. The enrichment technology is selected based on the set tasks. Recyclate quality for use alongside primary raw materials must guarantee refractory manufacturers meet the corresponding requirements of end-users. An original technology of recyclate enrichment during its selective grinding with product separation using air-gravitational and centrifugal-air classification has been developed