Evolution profile of gases during coal carbonization and relationship between their amounts and the fluidity or coke strength

Abstract

The evolution of inorganic-gases (H2, CO, CO2 or H2O) and hydrocarbon gases CH4, C2(C2H4, C2H6), or C3(C3H6 + C3H8) during the carbonization of caking coals is examined to clear the influence of the evolution amount of these gases on the Gieseler maximum fluidity (MF) and coke strength (DI15015). The samples are carbonized at 3 °C/min up to 1000 °C in high-purity He. The MF and the evolution profile of gases depend on the coal type. A negative relation exists between evolution amounts of gases, except for H2, until initial softening temperature (IST) and MF values. Additionally, the evolution amounts of inorganic gases, except for H2, until the IST increase with the increase of the carboxyl (COOH) group contents in raw coal. Moreover, the MF values trends to decrease with the increase in the COOH in raw samples. Thereby, it is found that the inherently-present coal-O adverse affect coal fluidity. Drum index (DI15015) of coke increases with the increase of C%-dry ash free (daf), fixed carbon (FC) %-dry, and reflectance (R0) vol% in raw coal, while the values decrease with the increase O%-daf and volatile matter (VM) %-dry. The DI15015 values exhibit an increasing trend with regard to the amount of the evolved H2 or CH4 during the carbonization. However, the values decrease as the amount of O-containing gases increased. A similar trend is observed in semi-coke and coke, where the values decrease as the remaining O% increased. Although the proportion of turbostatic-C (T-carbon) in coke depends on the coal type, DI15015 increases as the proportion of T-carbon increased. Therefore, it is found that the coal-O also has an adverse influence on coke strength.