Upgrading of Jatropha-seed residue after mechanical extraction of oil via torrefaction

This study examined the torrefaction performance of Jatropha-seed residue after mechanical screw-press extraction of oil (denoted as JME) at fixed torrefaction temperature (T_r) of 533, 553 and 573 K in the torrefaction time (t_r) range of 10–60 min. The characteristics results of torrefied JME (JME_T) indicated that the mass yield decreases while dry-basis high heating value (H_HD) increases with increasing T_r and t_r. At t_r = 20 min or longer and T_r of 533–573 K, the H_HD of obtained JME_T is suitable for B1/B2/D Taiwan power industry fuel requirement. In addition, the H/C and O/C atomic ratios of JME_T are better (i.e., lower) than those of torrefied wood and close to those of lignite and sub-bituminous coal. The satisfactory energy densification (E_D) of about 1.3 can be achieved for Case 1 at higher T_r of 573 K and shorter t_r of 30 min with log severity factor (logSF) of 7.37 or Case 2 at lower T_r of 553 K and longer t_r of 50 min with logSF of 7.00. The results indicated that Case 2 exhibits a lower value of SF than Case 1 at the same level of satisfactory E_D, which is more beneficial for the torrefaction of JME.