Benefits of using steel slag in cement clinker production for environmental conservation and economic revenue generation

Abstract

Steel slag, the most discharged metallurgical slag in China, is rarely applied in the production of clinkers. The aim of this study is to analyze the maximum substitution amount of steel slag in raw meal and calculate the resources required as well as the environmental and economic benefits of the addition. Numerical studies show that 14.30% was the maximum amount of steel slag added to the raw meal, and this was mainly determined by its Fe2O3 content. Pilot runs revealed that the quality indices of the currently used iron ore-based raw meal cannot be transferred to steel-slag-based feeds because the physical properties of the latter induce several technical problems during the production process. However, by implementing optimized quality indices and operational processes, the plant was able to produce a steel slag clinker with excellent performance, whose indicators all met the national standard requirements. It is possible to substitute all the iron ore (26.35–125.42 kg/t) and part of the limestone (34.40–160.02 kg/t) with increasing amounts of steel slag (from 43.04 to 202.26 kg/t). Using steel slag also led to an additional reduction in energy consumption (2.32–11.38 kg/t). Lessened limestone dissociation and lowered sintering temperatures can also help decrease the process and fuel emissions by up to 72.28 kg/t and 24.16 kg/t, respectively. Moreover, the use of steel slag can decrease raw meal cost by up to 0.82 USD/t compared to using iron ore and potentially increase annual earnings up to 2.37 MUSD/a for a 2500 t/d cement plant.