Evaluation of fuel properties and combustion behaviour of hydrochar derived from hydrothermal carbonisation of agricultural wastes

Biomass energy is an effective way to replace traditional fossil fuels. In this paper, hydrochar fuels were prepared using agricultural wastes (AW) from corn field at different hydrothermal carbonisation (HTC) temperatures. Their physicochemical properties, combustion characteristics, kinetic analysis and tendency of slagging and scaling were systematically investigated. The results showed that hydrochar had the highest energy yield of 68.54% when the HTC temperature was 220 °C. With the increase in HTC temperature, the H/C and O/C atomic ratios of hydrochar decreased, while the porosity increased first and then decreased. The higher HTC temperature was favourable for the formation of aromatic structures and unfavourable for the formation of oxygen-containing functional groups. As the HTC temperature increased, the Ti and Tb of hydrochar gradually moved to higher temperature range. The Coats-Redfern integration method was applied for the kinetic analysis of AW and hydrochar. The slagging and fouling indices of hydrochar were measured and indicated its low slagging and fouling tendencies, which are conducive to improving the heat transfer efficiency of the heat receiving surface. •Mechanism of hydrothermal carbonisation of agricultural wastes was proposed.•Hydrothermal carbonisation product has better combustion behaviour than feedstock.•Combustion kinetics of hydrochar fuels were analysed via Coats-Redfern method.•Hydrochar fuel shows low slagging and fouling tendencies.