Effect of ash and inorganic minerals in Dalita long-flame coal on biogas production

Abstract:

[Objective] This study focuses on investigating the effects of ash content and minerals in long-flame coal from Daliuta with different density biogas production by simulated gas production experiments with enriched cultures of anaerobic bacteria and archaea. [Methods] Daliuta long-flame coal was separated into different fractions by density with small floating sedimentation. The physiochemical properties of the coal fractions, including proximate analysis, XRD, and XRF were analyzed. These coal fractions were used to conduct biogas production experiments. The methane yield was used as an indicator to evaluate the effect of ash content on gas production in different coal fractions. The effect of minerals in coal was also investigated by amendments of commercial-grade minerals. [Results] It appears that the effects of ash content in coal on gas production is significant (P=0.035). i.e., ash content is negatively correlated to the methane yield. Moreover, minerals such as kaolin, siderite, and ferrous magnesium oxide in the ash could suppress gas production. Experiments with different mineral ratios confirmed that gas production was prominent with low content of clay minerals and restricted with high content of clay minerals. [Conclusion] The ash content of coals of different density generally has a significant effect on biogas production. The methane yield was low for high-ash coal and high for low-ash coal.

Key words:biogenic coal bed methane;low rank coal;ash;inorganic minerals;methane