The effects of hydrothermal dewatering on Indonesia lignite characteristics for fixed-bed gasification

Abstract

ABSTRACTHydrothermal dewatering of lignite derived from Pendopo, South Sumatera, Indonesia, was evaluated at residence time ranging from 30 to 90 minutes and size ranging from 1 to 7 cm, with a pressure of 30 bar and a temperature of 225°C. The total moisture (TM) content of the raw lignite was approximately 37.56 wt.%, the volatile matter content was 37.24 wt.%, ash content was 1.8 wt.%, fixed carbon content was 23.4 wt.%, and the calorific value (CV) was 3,337 kcal/kg. In addition, the thermal fragmentation of raw lignite was 42%. Lignite was hydrothermally dewatered with the addition of water in the laboratory scale. The solid products yield was between 48.00 and 57.88 wt.%, and the CV of hydrothermally dewatered lignite was between 4,781 and 5,308 kcal/kg. Meanwhile, the thermal fragmentation of HTD lignite was 0.1–1% and TM was 11.53–20.91wt.%. Change in the carbon-functional groups and their properties, as determined by Fourier-transform infrared spectroscopy, shows the significant decrease of hydroxyl group intensity that appeared in the region 3,100–3,600 cm−1, which was attributed to the dehydration phenomena. The HTD lignite has low water content and is resistant to thermal fragmentation, which makes it promising to be used as a fuel in the fixed-bed gasifier.