Experimental and simulation study of hydrochar production from cotton stalks

Cotton stalks (CS) are low-value agricultural residues which are usually burned in the fields, causing a major environmental problem. Bioenergy from agricultural residues has a two-fold advantage over other renewable energy sources: it allows for energy production as well as waste material recovery. In this work, the application of hydrothermal carbonization (HTC) to produce hydrochar from CS was investigated. The HTC experiments were carried out in a laboratory HTC reactor with an optical cell. The effect of reaction time was examined by altering it from 5 to 360 min at a constant temperature of 200 °C. It has been proven that hydrochar yields decrease and the heating value increases with an increase in reaction time from 5 to 360 min at 200 °C. The maximum higher heating value (20.41 MJ/kg) of hydrochar was obtained at 200 °C for 360 min. The highest degree of carbonization'of CS observed at 200 °C and a reaction time of 45 min and above. Furthermore, the experimental results were verified by mass and energy balances calculated with the simulation software IPSEpro. Based on these findings, a process sheet for an industrial application is suggested and calculated.