Abstract
To assess the thermal transformation process of common sulfide minerals in a nitrogen atmosphere, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and thermogravimetric mass spectrometry are employed to define the influence of the pyrrhotite content in pyrite-pyrrhotite mixtures (mixed minerals). The results indicate that an increase in pyrrhotite content decreases the temperature of the maximum mass loss rate of mixed minerals and reduces its mass loss. The solid-phase transformation of the thermal decomposition of mixed minerals is accelerated because the apparent activation energy of pyrrhotite is lower than that of pyrite and mixed minerals. However, the pyrrhotite makes the mixed minerals easier to sinter and agglomerate, which reduces the total volatilization amount of the gas product, S2; thus, the rate of mass loss decreases.
Highlights
Pyrite and pyrrhotite are common sulfide minerals in mines [1]
Researchers generally believe that the combustion and explosion processes undergo two stages: thermal decomposition and oxidation; the thermal decomposition process is consistent with the reaction in an inert atmosphere (N2, He, and Ar) [9,10,11]. erefore, studying the thermal decomposition process of sulfide minerals is of great value to reveal the mechanism of combustion and explosion
Considerable research has been carried out on the thermal decomposition behavior of pyrite in an inert atmosphere using a wide range of methods. Many of these results show that the thermal decomposition of pyrite is controlled by a chemical reaction and is a surface first-order reaction [12, 13]
Summary
Pyrite and pyrrhotite are common sulfide minerals in mines [1]. Pyrite (FeS2) is widely used in rubber and textile, pyrrhotite (Fe1-xs) is widely used in heavy-metal pollution control, and both of them are widely used in acid production industry [2,3,4,5]. Erefore, studying the thermal decomposition process of sulfide minerals is of great value to reveal the mechanism of combustion and explosion. It is considered that the thermal decomposition process is as follows: pyrite ⟶ pyrrhotite ⟶ troilite (FeS) ⟶ Fe, and this process is controlled by the temperature and total S gas pressure in the system [14]. The thermal decomposition of pyrite and pyrrhotite has been studied in detail, it is well known that the thermochemical reactions of mixed-mineral sulfide ores are more complex than those of single-mineral samples. E purpose of this study is to determine the influence of pyrrhotite content on the thermal decomposition reaction of pyrite-pyrrhotite mixtures (mixed minerals) as the basis for the step in revealing the combustion and explosion mechanism of the mixed minerals. E purpose of this study is to determine the influence of pyrrhotite content on the thermal decomposition reaction of pyrite-pyrrhotite mixtures (mixed minerals) as the basis for the step in revealing the combustion and explosion mechanism of the mixed minerals. erefore, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric mass spectrometry (TG-MS), and other characterization methods were applied to determine the causes of the influence by analyzing solid and gas products and calculating the apparent activation energy
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