Impact of chemical structure of coal on coke quality produced by coals in the similar category

In order to study the association of coke quality with the little fluctuation of chemical structure of the coal, three coals (C1, C2 and C3) from the similar category were employed to prepare coke in a 10 kg-scale coke oven. The status-oriented (G value, inorganic and organic component, etc.) and process-oriented (fluidity, volatile release, etc.) properties of the three coals are assessed. The association of coal chemical structure with these properties and final coke quality is clarified based on the experimental results by 13C NMR, Raman, etc. Clearly, the three coals from the similar category produce cokes with different properties. Chemical structure information obtained from 13C NMR and Raman shows that large aromatic clusters (higher far, Ca, etc.) with short chain hydrocarbon (lower CH2/CH3), and low graphitization degree (lower AG/AD, PG-D) of coal are not favorable for the coke strength. On the one hand, these structural properties determine the low vitrinite reflectance of coal and restrict the crosslinking reaction that may assist in the formation of the turbostratic carbon structures and affect coke strength. On the other hand, large aromatic clusters but short chain hydrocarbon are difficult to be depolymerized to form mobile components or transferable hydrogen-rich radical donor or acceptor. The development of the fluidity is insufficient to enhance coke strength, which is manifested by narrow plastic range, high temperature zone of thermoplastic stage, and low fluidity. In addition, defected structures (high GR+VL+VR and IGR+VL+VR/ID) in coal contribute to the high reactivity of corresponding coke. The unprotonated aromatic carbons (farN) may correspond to these defected structures in aromatic macromolecular. The results assist in establishing the association of apparent coal property and coke strength with coal chemical structure. The findings also support the assessment and prediction of coke strength for different coals, in particular, for coals that may fall into the similar category according to their similar apparent property.