Abstract
Research on the spontaneous combustion of coal caused by sulfur has always been focused on pyrite in coal but has rarely considered the influence of organic sulfur. In this paper, coal samples, rather than model compounds, were used to study the influence of organic sulfur content in coal on its spontaneous combustion process. The results of X-ray photoelectron spectroscopy and thermogravimetry, differential scanning calorimetry, and mass spectrometry indicate that organic sulfur in Shuiyu clean coal exists in forms of mercaptan, thioether, sulfone (sulfoxide), and thiophene. With the decrease of organic sulfur content, the characteristic temperature points and the peak values of the exothermic curves in the process of coal oxidation spontaneous combustion all shifted toward higher temperatures. The ignition activation energy of coal also increased, and the initial and peak gas evolution temperatures of the oxidation products shifted toward higher temperatures. These findings suggest that the reduction of organic sulfur content can inhibit the oxidation process and spontaneous combustion tendency of coal. This effectively reveals the mechanism of the spontaneous combustion of coal and is of great significance to future studies in this field.
Highlights
Accidents caused by the spontaneous combustion of coal could be severe, and the resulting losses of high-quality coal are financially significant
This study aims to reveal the actual influence of organic sulfur on the oxidative spontaneous combustion of coal
Organic sulfur in Shuiyu coking coal exists in forms of mercaptans, thioethers, sulfoxides, and thiophenes
Summary
Accidents caused by the spontaneous combustion of coal could be severe, and the resulting losses of high-quality coal are financially significant. Sulfur is a harmful element in coal, and it produces hydrogen sulfide (H2S) and sulfur dioxide (SO2) in the combustion process, causing environmental pollution, but is important in restricting the utilization of coking coal resources (Li et al, 2018). Sulfur components in coal may be divided into two categories: inorganic and organic. Mainly in the form of mineral sulfur, such as pyrite, can be removed by washing. Organic sulfur is generally found within the molecular structure of coal in the form of carbon–sulfur (C–S) bonds. The removal of organic sulfur has always been a major problem in the field of clean coal utilization (Borah and Baruah, 1997; Huffman et al, 1985; Huggins et al, 1983)
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