Controlled microwave drying of zinc-bearing blast furnace dust for moisture-risk control and resource-recovery pretreatment.

Zinc-bearing blast furnace dust is an important secondary resource, but residual moisture can increase storage instability, corrosion, and handling risks before downstream resource recovery. This study investigated controlled microwave drying of blast furnace dust in a laboratory-scale 2.45 GHz cavity using single-factor experiments and a three-factor response-surface design. The effects of initial moisture content, microwave power, and bed loading were evaluated using moisture-ratio evolution, average drying rate, surface-temperature histories, dielectric measurements, and qualitative post-drying characterization. Increasing microwave power from 160 to 480 W shortened the drying endpoint from 450 to 150 s and increased the average drying rate from 2.7×10-4 to 8.1×10-4 g/g/s. Increasing the initial moisture content from 0.04 to 0.12 d.b. increased the average drying rate from 1.6×10-4 to 4.5×10-4 g/g/s, whereas increasing the initial mass from 10 to 30 g reduced it from 6.7×10-4 to 4.4×10-4 g/g/s. The response-surface model yielded an R2 of 0.9745 and a predicted R2 of 0.9369. The model-predicted operating condition was 0.12 d.b., 480 W, and 10 g, with a predicted average drying rate of 7.2×10-4 g/g/s. The Modified Page model provided the best empirical description of MR(t), with R2 values close to 0.997 under representative conditions. No visible arcing or ignition occurred within the investigated operating window. These results support controlled microwave drying as a moisture-risk-control pretreatment for zinc-bearing blast furnace dust before downstream resource recovery.