Effects of Rapid Preheating on Coal Structure and Coke Strength

Abstract

At present, a rapid preheating process of coals prior to coke ovens is under investigation in the national project (SCOPE21). The effects of the rapid preheating of coals on the coal chemical structures and the resultant coke strength have been examined in the present study.
The cracking reactions of the coals appeared to be suppressed in the case of the rapid preheating (10⁴°C/min) of the coals up to their softening temperatures, compared to slow preheating (10°C/min): the ratios of O/C and H/C in the rapidly preheated coals were found to be almost identical to those of the untreated coals. The NMR study revealed the enhanced mobility and structural relaxation of the coal molecules due to the rapid preheating.
The rapid preheating of the coals improved the resultant coke strength. The enhanced mobility of the coal molecules, observed in the present study, is thought to improve the thermoplasticity of the coals at the melting stage, which lead to the improved strength of the resultant cokes.
The effect of CO₂ and H₂O gas in the preheater on the resultant coke strength was studied. The estimated concentrations of CO₂ and H₂O gas was found to hardly oxidize the coals in the preheater.
In conclusion, the rapid preheating process of coals is thought to be effective to improve the resultant coke strength.