Reactivation and utilization study of melting furnace slag generated from co-processing MSW incineration fly ash

Melting furnace slag (MFS) is a potentially active by-product of the synergistic treatment of iron and steel dust sludge and Municipal Solid Waste (MSW) incineration fly ash in the flue gas magnetization fusion separator furnace of the “fire method + wet method”. This paper focuses on the MFS reactivated by mechanical grinding, and the reactivity of MFS is synergistically enhanced by alkaline, sulfate-based solid wastes. The particle size distribution, specific surface area, morphology, and physical phase composition of MFS with different grinding times resulted in the best performance of MFS when mechanically ground for 80 min and the specific surface area reached 450 m²/kg, and the reactivity indexes reached 100.94% and 103.7% for 7 and 28 d, respectively. The synergistic activation of steel slag and flue-gas desulfurization gypsum can play an effective role in stimulating the MFS, and the optimal proportion is m (MFS): m (SS): m (FGDG) = 42%: 42%: 16%. The reactivity enhancement mechanism of the ternary slag-based system on MFS: SS provides high alkalinity hydration reaction conditions for MFS and FGDG provides SO₄²⁻, which continuously promotes the hydrolysis of MFS under the synergistic reactivity stimulation to generate AFt and C–S–H gels.