Effects of process conditions on calorific value and yield of charcoal produced from pyrolysis of coconut shells

Charcoal, a black carbon residue, is mostly produced from the major conventional method where the biomass is allowed to be heated for several days in a kiln without studying the process condition. Most of the studies on the pyrolysis process focus on the liquid and gaseous by-products neglecting the solid to be used as a combustion fuel. For this study, charcoal was produced from coconut shells by the thermochemical conversion method of pyrolysis in a controlled nitrogen environment at temperatures of 300 °C, 400 °C, and 500 °C, and residence times of 15 min, 30 min, and 60 min. This was conducted to evaluate the process conditions’ effects concerning the charcoal calorific value and yield. From the results obtained, a high process condition increases the calorific value, which results in a decrease in the charcoal yield. The lowest temperature gives a yield of 70.18 wt% and calorific value of 25.30 MJ/kg while the highest temperature produces a yield for as low as 26.57 wt% and a high calorific value of 30.15 MJ/kg. Furthermore, the charcoal yield tends to decrease from 51.99 to 33.10 wt% and the calorific value increases as the residence time increases from 15 to 45 min. Consequently, the thermal conversion undergone by the biomass may cause the changes of the quality parameters. Thus, charcoal can replace the use of fossil fuels because it presents energy content higher than that of lignite and similar to that of coal.