3.2. Pyrolysis process

Pyrolysis is a thermal treatment with limited oxygen by which organic materials are chemically decomposed by heat. It is a promising method by using waste materials such as biomass as feedstock to convert waste into energy and other valuable products. During the pyrolysis, large molecules break down into small molecules, resulting in carbonaceous materials, combustible gases, and condensable liquid hydrocarbons for renewable energy resources [39–42]. According to Sienkiewicz et al. [43], it is obvious that there is a significant potential of pyrolysis treatment based on ongoing works along with increasing cost of energy and petroleum and resources such as carbon black.

The pyrolysis of coconut shell was performed in a Carbolite 11/150 laboratory scale rotary furnace (Carbolite, Hope Valley, UK) situated in a walk-in fume cupboard. As shown in Figure 3, a rotatory horizontal tubular quartz vessel with the capacity of almost 5 liters is suspended by air-tight rotary fixtures inside an electrically heated box-furnace. According to several studies, the rotation rate is set as 10 ramp/min. The temperature is controlled at 600C by the thermal system with a thermocouple in the box furnace. Nitrogen gas is introduced into the reaction vessel from the gas inlet ports at 550 ml/min flow rate [44]. The nitrogen flow maintaining in the vessel throughout the pyrolysis is to protect the char from oxidation and help to carry and remove the pyrolytic volatiles (oil and gas) toward the oil trap. At the same time, the noncondensable volatiles (gases) were vented from a small opening on the top of the oil trap to the fume cupboard.
