Effect of binder composition on the preparation of formed coke with low-rank coal

Formed coke was prepared using low-rank coal as the main material and asphalt, heavy oil, and coking coal as the binder. The effects of the briquette compressive strength, pyrolysis product yield, and binder composition on formed coke were mainly studied. The shape, appearance, and structure of formed coke and composition of coal tar were analyzed through scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and gas chromatography-mass spectrometry(GC-MS). Results indicated that asphalt was the key component that influenced the formed coke compressive strength. Moreover, the yield of formed coke gradually decreased, whereas the compressive strength gradually increased as the amount of added asphalt increased. When the asphalt addition was 20%, the formed coke compressive strength reached a maximum of 18 MPa. The yield of pyrolysis gas slowly increased, while the H-2, CO, and CH4 contents in the gas were gradually reduced. FT-IR analysis shows that the absorption intensity of hydroxyl, carbonyl, and carbon-carbon double bond increased with asphalt addition. The heavy oil and coking coal exhibited high hydrogen content and H/C atomic ratio, which strengthened the function of hydrogen supply in the coal pyrolysis process, thus promoting hydrogen and hydrocarbon radical preferential binding. This binding is helpful in the production of light products that convert tar to light aromatics. With the addition of heavy oil and coking coal, the C6-10 component of coal tar increased, although the C11-19 component decreased.