Chemical Properties of Superfine Pulverized Coal Particles. 3. Nuclear Magnetic Resonance Analysis of Carbon Structural Features

The novel superfine pulverized coal combustion technology shows plenty of advantages, and a complementary description of the representative molecular structures plays a paramount role in better understanding its utilization processes. In this work, the carbon skeletal features of superfine pulverized coal were elucidated through C-13 NMR analysis. The changes of the coal chemical properties after the demineralization treatment were characterized. Furthermore, the influence of particle size on coal molecular structures was focused on, and the detailed evolution mechanisms were discussed based on the structural and lattice parameters. The final results indicate that decreasing particle size engenders the local coal maturation due to the thermal and mechanical strain effects. The oxygen-substituted aromatic carbon increases in smaller coal fractions at the expense of. oxygenated aliphatic carbon. Additionally, the oxidation effect of atmospheric oxygen during the superfine comminution is confirmed. Furthermore, the acid treatment promotes the cleavage of certain chemical bonds, which imposes a significant influence on the attachments and oxygen-containing groups in coal. In all, this research provides some new insights into, the role of mechanochemical effect during the coal comminution and is helpful for better understanding the coal chemical structures at a molecular level. The data obtained here will promote the development of the representative molecular models of superfine pulveriied coal, and improve the prediction of its behavior during practical application.