Characterization and optimization of the heat treatment of cashew nutshells to produce a biofuel with a high-energy value

Abstract

In the context of the fight against climate change and the development of renewable and new energies, the management of cashew nutshells is an issue. The physico-chemical and energetic properties of cashew nutshells show that they are good raw materials that can be used in thermochemical processes. Cashew nutshells were heated to temperatures of 300 ℃, 350 ℃ and 400 ℃ for 40 to 120 minutes to extract the liquid from the cashew nutshells. Biochar yields by mass were 46.5–52.8 wt%, 46.2–35.9 wt% and 37.8–30.3 wt% at temperatures of 300 ℃, 350 ℃ and 400 ℃, respectively. Biochar with high higher heating value and low residual oil content was obtained at a heating temperature of 300 ℃ for a time of 120 min. The biochar obtained under these optimum conditions has a residual oil content of less than 1 wt% and a higher heating value of 32.1 MJ·kg-1. The other two products, bio-oil and smoke, have higher heating values of 36 MJ·kg-1 and 10.2 MJ·Nm-3, respectively. Temperature and heating time improve the energy density and quality of biochar with low residual oil content. Heat treatment is therefore a promising technique for the production of an environmentally friendly and sustainable high energy solid biofuel from cashew nutshells.

Keywords

• cashew nutshells
• biochar
• cnsl
• gas
• heat treatment