Hydrothermal Carbonisation of Australian Saltbush

Hydrothermal carbonisation (HTC) is a thermochemical process wherein biomass is subjected to high-pressure, high-temperature subcritical water to improve the combustion characteristics of biomass as a solid fuel. Australian saltbush was subjected to HTC at three temperatures (200oC, 230oC, 260oC) and four holding times (0 min, 15 min, 30 min, 60 min), using a custom-built batch reactor. The resultant hydrochars demonstrated improved higher-heating values, with temperature more influential than time. At the most severe condition of 60 minutes, 260oC, the hydrochar possessed numerous key similarities to fossil coal, such as a higher heating value of 27.5MJ/kg, similar ratios of carbon/oxygen and hydrogen/oxygen, and equivalent levels of volatile matter, fixed carbon and ash. The HTC process also proved effective in reducing the high levels of inorganic elements naturally present within saltbush, with 60 minutes at 260oC again shown to be the most effective condition, removing almost 95% of sodium, chloride,...