Efficient utilisation of waste steel slag in slag-making process of all-scrap electric arc furnaces

A novel technique to recycle waste steel slag is to optimise the foam slag process of all-scrap electric arc furnaces (EAFs). The influence of waste steel slag addition on the basicity of final slag was studied, as slag basicity significantly affects foaming performance. The minimum control requirement of not less than 1.8 was obtained to calculate the maximum mass of waste steel slag. The above results were obtained through the use of thermodynamic calculation software Factsage8.3 and theoretical calculations. The properties of the foam slag were investigated, revealing improved effective viscosity. The optimised foaming index ranged from 2.27 to 2.65 s, compared with 1.63 to 2.45 s before optimisation. The optimisation was achieved by controlling the amount of waste steel slag and other additives, as well as the usage of oxygen and carbon powder. The average consumption reduction of oxygen, carbon powder, and electricity was 2.68 Nm 3 /t steel, 1.12 kg/t steel and 10.12 kWh/t steel in the industrial trials, respectively. The degree of metallisation has increased due to the reduction in oxygen consumption and slag production. It was observed that waste steel slag can be recycled successfully as an additive on an industrial scale.