Pyrolysis behaviors of waste coconut shell and husk biomasses

Abstract

Coconut shell and husk are two biomasses wastes abundant in most of the coastal countries. However, despite their enormous potential as energy sources, they are hardly studied and their thermal characteristics are still not well known. In this study, both biomasses are thermally degraded through thermogravimetry (TG-DTA) and their pyrolysis product yield such as char, tar and gases are analyzed. The TG-DTA results show that pyrolysis of biomass consists of three stages. Three stages can be outlined as: (1) dehydration process for temperatures below 122°C, (2) pyrolytic cracking from 122°C to 400°C, stage consist of two exothermic simultaneous processes where hemicelluloses, cellulose and lignin are decomposed and a high amount of volatile matter formation occurs and (3) the last endothermic decomposition of the lignin at temperatures above 400°C. From the pyrolytic results, it is showed that the char and gases yields were increased with the decrement tar. The gas-evolving profiles from pyrolyzing the coconut shell and husk components in a packed bed, monitored by a GC-TCD and a GC-FID, showed similar behavior. H2 was released out at a higher temperature (>450°C) and it got the maximum rate at 700°C then it decreased. CO2 was released out at 130°C–750°C and got the maximum releasing value at 300°C–400°C. The released CO showed almost similar pattern with that of CO2. However, the release rate was lower than CO2 and the maximum release rate of CO was found at 300°C –400°C. CH4 was released out at the temperature between 200°C –850°C, and it got the maximum rate at 550°C. The releasing of hydrocarbon was generally very low.