Mechanochemical effect of spontaneous combustion of sulfide ore

Abstract

Spontaneous combustion of sulfide ore is a typical disaster in mining, which can cause a series of environmental and safety problems. In order to reveal the mechanical activation’s influence on the spontaneous combustion of sulfide ore during the mining process, the changes in the microstructure of sulfide minerals and their spontaneous combustion kinetics before and after activation were studied in this paper. The most probable mechanism function, apparent activation energy, and pre-exponential factor were derived using the Malek and Friedman methods, respectively. The results showed that mechanical activation leads to aggregation of mineral particles, defect generation in crystals, reduction in crystallize size, and increase in lattice distortion rate, which result in samples more actively. In the process of oxidation and spontaneous combustion, the main products were Fe2O3 and SO2 gas. And the mechanochemical effect will cause the reaction rate to become faster and lead the reaction to move toward low temperature. The mechanochemical effect will also lead to chemical reactions at low temperatures, causing some ore samples to be oxidized without changing the samples’ reaction mechanism functions. After mechanical force, the average apparent activation energy decreased by 26.27 kJ/mol, 32.73 kJ/mol, 27.01 kJ/mol, and 35.30 kJ/mol, respectively, and the sample’s spontaneous combustion tendency increased. In addition, ore samples’ active surface and grain boundary area increased under the mechanical forces, the lattice was distorted and dislocated, and a sub-stable amorphous phase was formed. In this process, the mechanical energy was partially converted into energy storage in the solid material, significantly increasing reactivity.