High-strength charcoal briquette preparation from hydrothermal pretreated biomass wastes

The waste cotton stalk (CS) and wood sawdust (WS) biomass samples pretreated by two different thermal methods (dry torrefaction (DT) and hydrothermal treatment (HT) at 200, 230, 260 °C, respectively) were densified to prepare biomass briquette and then carbonized at 400 °C to prepare charcoal briquette without any binders. The physical properties and combustion characteristics of the derived charcoal briquettes were investigated to assess the feasibility of its application as barbecue charcoal. The results indicate that the physical properties including the mass densities and compressive strengths of HT charcoal briquettes are better than those of DT and unpretreated charcoal briquettes, even those of the commercial barbecue charcoal with binder addition. Moreover, the fixed carbon and ash yields of the resulted HT charcoal briquettes meet the European Standard on commercial barbecue charcoal. Especially HT charcoal briquettes has far lower ash yield than the commercial barbecue charcoal. HT charcoal briquettes have similar combustion character index (S) with the commercial barbecue charcoal. In the research, CS and WS hydrothermal pretreated at 230 °C are the best materials for the charcoal briquette preparation process.