Thermogravimetric analysis of combustion characteristics and kinetics of hydrothermally treated and washed empty fruit bunch

Abstract

This study aims to study the fuel properties, combustion behaviors and kinetics of hydrothermally treated and washed empty fruit bunch (HTW-EFB). For the lab-scale samples, EFB was hydrothermally treated (HT) at 180, 200 or 220 °C for 30 min and washed using water at 60 °C for 15 min to remove alkaline metals. For the commercial-scale sample, EFB was HT at 2 MPa for 30 min and washed with room temperature water using a centrifugal machine. Results indicate that a combination of hydrothermal and washing treatments (HTW) improved fuel properties of EFB significantly, with an increase in calorific value to 2.33 × 10⁴ kJ kg⁻¹ and a reduction in the alkaline contents. Significant shifts in combustion behavior were observed when EFB underwent HTW. The ignition temperature of the hydrochars was 290–296 °C with the burnout temperature at 438–485 °C. From the kinetic study, a first-order reaction and one-dimensional diffusion is the main mechanism in the combustion of volatiles, while one-dimensional diffusion is the main mechanism for the combustion of the fixed carbon of the hydrochars. The activation energy of HTW-EFBs was between 99.96 and 138.26 kJ mol⁻¹ in the devolatilization stage and 10.97–27.56 kJ mol⁻¹ in the char oxidation stage.

Keywords:

• Empty fruit bunch
• hydrothermal treatment
• water washing
• thermogravimetric analysis
• kinetics

Disclosure statement

No potential conflict of interest was reported by the authors.