Evaluation of wet torrefaction hydrochars as fuel for chemical looping combustion

Abstract

This study evaluated the potential of wet torrefied hydrochars as fuel in chemical looping combustion. Wet torrefaction of empty fruit bunches and oil palm trunks was performed at 180 and 220 °C for durations of 15 to 30 min at the biomass-to-liquid ratio of 1:25. Additionally, the effect of levulinic acid as the catalyst at different concentrations (0.1 and 1.0 M) was investigated to assess the acid catalysed hydrochars’ potential as fuel in chemical looping combustion. Characteristics of the hydrochars were elucidated to provide insights into their physical and chemical properties. The chemical looping combustion was simulated using thermogravimetric-mass spectrometry under oxidative conditions to replicate the fuel reaction phase of chemical looping combustion by oxygen carriers. Wet torrefaction of empty fruit bunches (EFB) and oil palm trunks (OPT) at 180 °C for 15 min without a catalyst produced hydrochars with high energy yields 62.64 % and 63.16 %, respectively. The hydrochars with the higher energy yield and an equal blend of the two were selected for further analysis using thermogravimetric-mass spectrometry. The thermogravimetric-mass spectrometry analysis revealed positive synergistic effects in the hydrochar blend. This could be attributed to the catalytic influence of metal oxides formed from the ash content during oxidative combustion. Wet torrefaction plays a crucial role in removing metals such as potassium (K), which can assist in reducing corrosion and fouling in the reactor.