Yuna Zhao

Reduction of low-grade manganese dioxide ore pellets by biomass wheat stalk

An investigation on reducing low-grade manganese dioxide ore pellets was carried out by using wheat stalk as reductant. The main impact factors of reduction percent such as particle size, biomass/ore ratio, heating rate, nitrogen flow rate, temperature and time in reduction process were discussed. The morphology and component of manganese dioxide ore particle at different stages were also analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results show the increase of the reduction temperature and time, biomass/ore ratio, and the decrease of particle size, heating rate and nitrogen flow rate can significantly enhance reduction efficiency. The reduction kinetic of the manganese ore is controlled by three-dimensional mass diffusion of gaseous reductive volatiles passing from the surface to the core of the ore particles. The activation energy E and frequency factor A were calculated to be 24.15 kJ·mol−1 and 166 min−1, respectively. Biomass pyrolysis volatiles adsorbed onto the surface of the ore particle leads to serious variation of the microstructures and chemical composition of the manganese ore particles.

Recovering indium with sulfating roasting from copper-smelting ash

Abstract A technology for recovering indium from Jinchuan copper-smelting ash was developed. Indium in the ash was first enriched to the leaching-slag in leaching process, and then recovered by sulfating roasting. The method included mixing the leaching-slag with sulfuric acid, making them into particles, roasting the mixture, and then leaching the calcine with hot water. Above 90% of indium in calcine could be dissolved into the leaching solution. The optimized conditions were determined as follows: the mass ratio of sulfuric acid to leaching slag was 0.1, the roasting time was about 1 to 1.5 h in the temperature range of 200–250°C, and the calcine was leached for 1 h with 5:1 of liquid/solid ratio at 60°C. Over 99% of indium in leaching solution was finally enriched by Zn substitution or sulfide precipitation.

Kinetics of recovering germanium from lignite ash with chlorinating roasting methods

Abstract A process of recovering Ge by chlorinating roasting was put forward. GeCl 4 was separated and recovered from lignite ash because of its low boiling point. Kinetic analysis indicates that the chlorinating roasting process fits with the unreacted-core shrinking model and the reaction rate equation corresponds to 1 − 2 a /3 − (1 − a ) 2/3 = kt . The apparent activation energy E a is calculated to be 22.36 kJ·mol −1 . The diffusion of product layer serves as the rate-controlling step in this process. When the roasting temperature is 250°C, the roasting time is 60 min, the concentration of hydrochloric acid is 10 mol/L, and the ratio of liquid to solid is 10 ( m HCl/ash = 10), and 90% Ge in lignite ash can be recovered.