Thermogravimetric and Kinetic Analyses of Oil Palm Empty Fruit Bunch (OPEFB) Pellets Using the Distributed Activation Energy Model

Bemgba Bevan Nyakuma,Arshad Ahmad,Tuan Amran Tuan Abdullah,Anwar Johari

doi:10.21315/jps2016.27.3.5

Abstract

The thermal degradation behaviour and decomposition kinetics of oil palm empty fruit bunch (OPEFB) pellets were investigated using a thermogravimetric analyser and the distributed activation energy model (DAEM). The OPEFB pellets were heated from 30°C to 1000°C at three different heating rates (5, 10, 20°C min-1) under a nitrogen atmosphere. The thermogravimetric-derivative thermogravimetric (TG-DTG) curves revealed that the non-isothermal decomposition of OPEFB pellets occurred in the following three stages: drying (35°C-175°C), active pyrolysis (200°C-370°C) and passive pyrolysis (370°C-1000°C), which resulted in the loss of moisture, volatile matter and char, respectively. The distributed activation energy model was subsequently used to determine the apparent activation energies (E) and pre-exponential factors (A), which ranged from 37.89 kJ mol-1 to 234.05 kJ mol-1 and from 2.05 × 102 min-1 to 3.54 × 1018 min-1, respectively, for conversions of α = 0.05-0.70 during the thermal degradation. The wide E and A distributions obtained from the kinetic analysis are attributed to the complex chemical reactions of pyrolysis. The kinetic analysis revealed the kinetic compensation effect (KCE), with the highest E and A values occurring in the range of α = 0.2-0.4. This result indicates that the active pyrolysis stage is the rate-determining step during the thermal decomposition of OPEFB pellets.

Highlights

Utilising biomass resources from the oil palm industry is a potentially viable route to clean, renewable and sustainable biofuels in the future.[1]
The thermal conversion efficiency of oil palm empty fruit bunch (OPEFB) pellets should be relatively high due to their low moisture content, and reactor operational problems due to sintering, agglomeration and corrosion should be minimised by their low ash content.[32]
The thermogravimetric-derivative thermogravimetric (TG-DTG) curves reveal that the OPEFB decomposition occurred in the following three distinct stages: drying, active pyrolysis and passive pyrolysis

Summary

Introduction

Utilising biomass resources from the oil palm industry is a potentially viable route to clean, renewable and sustainable biofuels in the future.[1]. Non-isothermal methods are more common due to their high sensitivity to experimental noise and low susceptibility to mass loss errors.[2,4] non-isothermal TGA requires fewer data points than isothermal TGA to investigate the solid-state decomposition kinetics of thermal conversion processes.[10] In addition, isothermal TGA analysis suffers from mass errors that occur due to ramping to the desired temperature during the analysis.[4] The thermal decomposition kinetics of algae,[3] wood,[11] orange waste[12] and agricultural residues[13,14,15,16] have been studied by non-isothermal TGA under inert conditions

Objectives

Results

Conclusion