Hydrothermal carbonization of multi-components in Biomass: Prediction and analysis of solid fuel properties

Biomass-derived fuels, as a renewable and carbon-neutral source of energy, hold significance to replaces fossil fuels and mitigates climate change for sustainable development. Among them, solid fuels via hydrothermal carbonization (HTC) have been recognized as one of the alternatives, which is derived from biomass wastes characterized by high moisture content and complicated compositions. However, owing to the diversity of various biomass, the fuel properties of hydrochars from different type of biomass (i.e., lignocellulosic or non-lignocellulosic types) exhibited huge difference. In this study, a series of HTC experiments were conducted on mixture of typical components (i.e., lignin, cellulose, protein, and so on) at varying ratios, and a modified prediction model was developed for the fuel properties of hydrochar and their synergies. Results show that positive synergies were found when the protein was added into lignocellulosic components, reaching synergistic coefficient of 47 %; between the lignocellulosic components, similar synergy could be found on the hemicellulose-lignin mixtures, although the synergistic coefficient was relatively low. Furthermore, the actual biomass was used to validated the prediction model established by mixture components, showing that the predicted values located within the 90 %–95 % confidence interval (CI) of the experimental values. This indicates that the mathematical prediction models possess good accuracy to evaluate the fuel properties of hydrochar from different type of biomass. Not only that, thermogravimetric (TG) analysis was performed on hydrochars derived from both actual and model biomass to explore the differences on the combustion behavior, which indicates that both of them exhibited similar mass loss behaviors and rates, further confirming the reliability of models. As a whole, the provided models can be applied to predict the fuel properties of hydrochars derived from the co-hydrothermal carbonization of different biomass components, holding significant importance for reducing experimental costs and facilitating the large-scale processing of biomass via HTC.