>> Steam gasification of low rank coals is possible at relatively low temperature and low pressure, and thus shows higher efficiency compared to high rank coals. In this study, the gasification reactivity of four different Indonesian low rank coals (Samhwa, Eco, Roto, Kideco-L) was evaluated in T = 700 -800°C. The low rank coals containing 53.8 ± 3.4 wt% volatile matter in proximate analysis and 71.6 ± 1.2 wt% carbon in ultimate analysis showed comparable gasification reactivity. In addition, K2CO3 catalyst rapidly accelerated the reaction rate at 700°C, and all of the coals were converted over 90% within 1 hour. The XRD analysis showed no significant difference in carbonization between the coals, and the FT-IR spectrum showed similar functional groups except for differences due to moisture and minerals. TGA results in pyrolysis (N2) and CO2 gasification atmosphere showed very similar behavior up to 800°C regardless of the coal species, which is consistent with the steam gasification results. This confirms that the indirect evaluation of the reactivity can be made by the above instrumental analyses.

>> The present work investigates the effect of K2CO3 catalyst on steam gasification of Kideco coal and the deactivation of the catalyst due to thermal exposure and interaction with coal ash. The gasification reactivity at 700°C is highly enhanced by K2CO3, which is not deactivated by the heat treatment at T ≤ 800°C. TGA and XRD results prove minor decomposition of K2CO3 after the calcination at 800°C. K2CO3 is, however, evaporated at the higher temperature. Assuming the conversion of K2CO3 into K2O by the decomposition and into K2O•2.5SiO2 and KAlO2 by the interaction with coal ash, the reactivity of the gasification is evaluated in the presence of K2O, K2O･2.5SiO2 and KAlO2. Among them, K2O is the most active, but much lower in the activity than K2CO3. XRD results show that K2CO3 could react readily with the ash above 700°C.