Effects of Water-Soluble Sodium Compounds on the Microstructure and Combustion Performance of Shengli Lignite

Abstract

Different water-soluble sodium compounds (NaCl, Na2CO3, and NaOH) were used to treat Shengli lignite, and the resulting effects on the microstructure and combustion performance of the coal were investigated. The results showed that Na2CO3 and NaOH had a significant impact on combustion performance of lignite, while NaCl did not. The Na2CO3-treated lignite showed two distinct weight-loss temperature regions, and after NaOH treatment, the main combustion peak of the sample moved to the high temperature. This indicates that both Na2CO3 and NaOH can inhibit the combustion of lignite, with the latter showing a greater effect. The FT-IR/XPS results revealed that Na+ interacted with the oxygen-containing functional groups in lignite to form a “–COONa” structure during the Na2CO3 and NaOH treatments. It is deduced that the inhibitory effect on combustion of lignite may be attributed to the stability of the “–COONa” structure, and the relative amount is directly correlated with the inhibitory effect. The XRD/Raman analysis indicated that the stability of the aromatic structure containing “–COOH” increased with the number of “–COONa” structures formed. Additionally, experiments with carboxyl-containing compounds further demonstrated that the number of oxygen-containing functional groups combined with Na was the main reason for the differences in the combustion performance of treated lignite.

Effect of ionic liquids on the microstructure and combustion performance of Shengli lignite

“… 23 However, due to the fluidity of air and water, the inhibiting time of this inhibitor is not long, and continuous inhibition of spontaneous combustion has poor efficacy. 24 Sodium phosphate, ammonium salts, antioxidants and other inhibitors can be used to interact with the active groups on the lignite surface to reduce the number of active groups or inhibit free radical reactions. However, these inhibitors do not consider the changes in the functional groups in coal based on its structural diversity.…”