Microwave drying process and mechanism analysis of viscous germanium-containing residue

Tannin germanium residue (TGR), which has high viscosity and water content, is one of the most important germanium-containing enrichments in the germanium extraction process. In this study, the microwave drying process of a TGR was studied using a high-temperature dielectric testing device, combined with a thermal drying analysis method and response surface methodology (RSM). The experimental results indicated that the water in TGR consisted of free water, crystalline water, and structural water. Owing to the excellent dielectric properties of water in TGR, microwave drying can save 91.7% of the drying time compared to the conventional method. Under the optimal microwave drying conditions, the dehydration rate of TGR was 40.3%. Microwave drying is advantageous in increasing the specific surface area of the TGR particles by 50.75% and pore volume by 160.42%. The high temperature dielectric properties and thermogravimetric curve analysis of raw materials showed that the dielectric constant of water contained in TGR was 12.5 times that of other components, and microwave drying saves 91.7% of the drying time compared with conventional drying. BET analysis showed that the specific surface area of microwave drying TGR increased by 50.75% and the pore volume increased by 160.42% compared with conventional drying. When the microwave power is 225 W and the drying time is 7 min, TGR has the best drying effect, and the germanium concentrate prepared by roasting has no overburning phenomenon.