Application of Hydrothermal Carbonization to Improve the Energy Properties of Peat

Abstract—The influence of the process conditions of hydrothermal carbonization (temperature, process duration, the presence of a catalyst (citric acid), and the raw material/water ratio) on the properties of hydrochar obtained from peat was studied. The following regularities were found: the weight and energy yields of the hydrochar decreased with the temperature and reaction time. An increase in the reaction temperature from 170 to 230°С contributed to an increase in the calorific value (from 23.86 to 26.8 MJ/kg for the gross calorific value and from 22.26 to 25.02 MJ/kg for the net calorific value). An increase in the reaction time from 1 to 6 h also led to an increase in the calorific value (from 22.72 to 24.61 MJ/kg for the gross calorific value and from 24.61 to 23.20 MJ/kg for the net calorific value). The addition of a catalyst increased the gross and net calorific values of hydrochar by 6 and 6.2%, respectively.