Hydrothermal Treatment of Herb Residue for Solid Fuel Production

Hydrothermal processing is appraised as one of advanced technologies for wet solid waste handling. In this study, herb residue was subjected to hydrothermal treatment. Calorific value, yield, and also proximate analysis of obtained hydro-char were investigated. A cylindrical reactor with an internal volume of 2.5 Litres made of stainless steel and a low-tech component was used in the experiment. The reactor was equipped with a stirrer to ensure heat transfer took place through the entire parts of the solid-water mixture. Solid products were dried by a microwave oven before analysis. The results show that the final temperature, holding time, and solid-water ratio have various effects on the hydro-char yield, calorific value, and proximate analysis of the hydrothermal products. The hydro-char yield decreased with the increase in final temperature and holding time. Meanwhile, the highest hydro-char yield was obtained at the solid-water ratio of ¼. The hydro-char calorific value increased with the increase in final temperature, holding time, and solid-water ratio. The rise in final temperature, holding time, and solid-water ratio resulted in a lower moisture content and volatile matter but higher fixed carbon. Meanwhile, the ash content increased with the solid-to-water ratio.