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Biomass can be upgraded via torrefaction, and torrefied kenaf (TK) is a fuel that allows blending with coal at high ratios. In the present study, raw kenaf (Hibiscus cannabinus L.) (RK) was torrefied at 523 K for 30 min and then mixed with Vietnamese anthracite (NinhBinh, NB) before co-pyrolysis. Thermogravimetric (TG) analysis was used to evaluate the behavior of RK, TK, and blended RK/TK during co-pyrolysis at biomass blending ratios (BBRs) of 0, 25, 50, 75, and 100 wt %. The TG and derivative thermogravimetry curves of a mixture of NB and RK (NBRK) were similar to those of RK. The decomposition curves of a mixture of NB and TK (NBTK) depended on the mass fraction of TK. Based on weight loss differences between the experimental and calculated data for the fuel blends, no interaction between the RK and anthracite was observed for all BBRs, whereas anthracite involving 50 and 75% TK exhibited synergistic effects. The temperature range for synergy and degree of synergy for NB and TK depended on the heating rate and mass ratio of TK. Kinetic parameters were calculated using the Friedman−non-isothermal free kinetic method at heating rates of 10, 20, and 40 K/min. The results showed that the activation energy (E) values of the NBRK at conversion ratios of 0.2−0.5 were equal to those of the RK, whereas they were superior at NB decomposition ratios of 0.6−0.8. NBTK1-1 (BBR of 50%) showed E values higher than those of NB at some conversion ratios, thus demonstrating a negative impact of blending. Further, NBTK1-3 (BBR of 75%) and NBTK3-1 (BBR of 25%) exhibited E values between those of NB and TK. The present study suggests that a high TK mass fraction (75%) in the blend for co-pyrolysis is optimal for the activation energy and volatile matter yield.

Torrefaction is an appealing pretreatment method for improving the fuel properties of kenaf biomass before its utilization in thermochemical processes. This study evaluated and compared the impact of torrefaction on thermal behavior and kinetics during pyrolysis and gasification. Thermogravimetric analysis experiments were conducted at temperatures of 300–1173 K at several heating rates under N 2 and CO 2 atmospheres. The raw and torrefied kenaf (RK and TK) during CO 2 gasification in the low-temperature region (<900 K) was found to exhibit a tendency that was similar to that of N 2 . However, TK during CO 2 gasification resulted in a lower maximum mass loss rate, delayed initiating temperature, and lower devolatilization index due to lower reactivity. In addition, the gasification reaction of CO 2 and char was observed to occur in the high-temperature region (> 900 K), thus improving conversion efficiencies. The activation energy for TK in a CO 2 atmosphere depending on the conversion was calculated using the distributed activation energy method. The activation of RK during CO 2 gasification was higher than that of N 2 . However, TK during CO 2 gasification exhibited a lower activation energy compared to that of N 2 , indicating its potential as a better feedstock during the CO 2 gasification process and the ability to save energy.

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