Evolution of carbon structure and cross-linking structure during coking process of coking coal

Abstract

Considering the sustainable development of resources and environmental protection, realizing the utilization of coal cleanly and effectively becomes an important issue. An in-depth understanding of the changes in the structure of coking coal in the coking process is conducive to improving the quality of coke, promoting the development of the coal chemical industry, and realizing the clean and efficient use of coal. The coking products of Guanyintang coking coal, Matou coking coal, Wugou fat coal, Xiaoxian fat coal, and Yanzhou West gas coal with different metamorphism degrees were analyzed by X-ray photoelectron spectroscopy (XPS) and High-Resolution Transmission Electron Microscope (HRTEM) from 600 °C to 1000 °C. The results of XPS showed that as the coking temperature increased, the relative content of graphitized carbon structure and aliphatic carbon structure gradually increased and decreased, respectively, and the relative content of oxygen-containing functional groups (C-O, CO, and COO-) showed an overall decreasing trend, Yanzhou West gas coal had the highest percentage change in sp2 of 18 %. Sample MTJM had the least percentage change in sp2 of 13 %. The results of HRTEM showed that the interlayer spacing and the length of the aromatic layers decreased and grew, respectively. The degree of mean tortuosity decreases with the increase in coking temperature. The extension and flattening trend of aromatic layers were closely related to the condensation of aromatic rings during the coking process.