Pyrolysis of hydrochar derived from biomass – Experimental investigation

Abstract In this study three kinds of biomass were investigated: wood biomass (pine), energy crop (Sida hermaphrodita) and agriculture biomass (straw) using the hydrothermal carbonization process (HTC). The HTC process was conducted in a specially designed reactor under the following conditions: 220 °C temperature and 4 h residence time. The solid (hydrochar) and liquid products of hydrothermal conversion were determined in terms of their chemical and physical properties. Futhermore, the basic parameters of the obtained hydrochars were established: ultimate and proximate analyses, higher heating value, mass and energy yield and energy densification ratio. The liquid products were analysed by measuring pH and conductivity, which confirmed their acidic and polar character, and Chemical Oxygen Demand (COD) at very high value indicating that the liquid phase contained a high concentration of organic matter and nutrients. Additionally, the TGA of hydrochar was performed in an air and inert atmosphere to simulate the combustion and pyrolysis process. Moreover, the pyrolysis process of the hydrochars was investigated using Py-GC-MS apparatus. The process was performed to analyze the composition of pyrolysis products from the hydrochars. The samples were pyrolyzed in sequence at 400, 500, and 600 °C with rapid heating and a short residence time. The pyrolysis of the hydrochars resulted in varied organic compounds dependent on the pyrolysis temperature and chemical composition of hydrochars.