China Nonferrous Metallurgy

Aiming at the problems of long drying cycle and large process pollution of the current lead-zinc smelting slag, this paper proposes a new technology of microwave enhanced drying. On the basis of analyzing the physical properties of the raw materials, the high temperature dielectric and microwave drying factors of the neutralized lead-zinc smelting slag were analyzed, and the drying process mechanism of the microwave-enhanced neutralized lead-zinc smelting slag was clarified. The results show that the phase containing crystal water in the neutralized slag is CaSO₄·0.5H₂O, the content of free water is 30.2%, and the content of crystal water is 7.2%. The wave-absorbing properties of free water and crystal water are similar, and obviously superior to other phases in slag. Under the conditions of particle size 8cm, thickness 2.2cm, microwave power 700W, and drying time 15min, microwave drying has the best effect of neutralized lead-zinc smelting slag, free water is completely removed, the removal rate of crystal water reaches 53.06%, and the total water loss rate is 34.02%. When the neutralized lead-zinc smelting slag is dried by microwave, it will cause cracking and stratification of the neutralized slag, which helps to achieve fast and efficient drying. Compared with conventional drying, microwave drying 1kg neutralized lead-zinc smelting slag saves energy by 16.98% (630kJ), removes 5.40% more water than conventional drying, and shortens drying time by 87.5%. The drying technology of neutralizing lead-zinc smelting slag established in this paper has obvious advantages.