Physico-mechanical properties and thermal decomposition characteristics of pellets from Jatropha curcas L. residues as affected by water addition

Abstract

Fruit hulls and seed shells from Jatropha curcas L. are considered valuable biomass residues to be used as fuel. In this study, J. curcas hulls and shells were blended and pressed into pellets. Different amounts of water were added to the raw materials before pelleting (0, 5, 10 and 15 g/100 g fresh matter) to improve the pellet durability. The outlet temperature of the pellets was inversely proportional to the amount of water added to the raw material. The thermal decomposition of all pellets showed typical decomposition kinetics between 180 and 500 °C. Moisture content, ash content, calorific values, dimension and solid density of the pellets fulfilled German standard requirements for commercial pellets, but not for highly durable pellets. The static and dynamic angle of repose and coefficient of static friction of the pellets were also studied. Bulk density and porosity were considerably influenced by water addition. To some extent, pellet durability was improved significantly (p ≤ 0.05) by water addition, whereas the highest abrasive resistance of pellets was achieved by the highest water addition. Jatropha curcas pellets have a good potential as a solid biofuel and a raw material for biochar production.

Keywords:

• Densification
• mechanical properties
• physical properties
• thermogravimetric analysis
• tumbling
• quality

Acknowledgements

The authors thank Mr. Dino Tomazic for his technical assistance. Funding for this research was provided by Bundesministerium für Bildung und Forschung (BMBF), Berlin, Germany. This investigation was carried out under Project 033R069A, Integrated Jatropha curcas de-hulling, de-shelling, de-oiling and detoxification process for efficient production of high-grade designer protein feed and plant oil.