Date of Award

2-23-2022

Thesis Type

PhD

Document Type

Thesis

Divisions

Faculty of Engineering

Department

Department of Chemical Engineering

Institution

Universiti Malaya

Abstract

Empty fruit bunches (EFB) have great potential to be used as a renewable fuel. Its current low rate of utilization due largely to high moisture content and low calorific value (CV) can be overcome via a thermal pretreatment namely torrefaction. This study investigated the effects of torrefaction temperature, residence time, particle size and moisture content on EFB’s final products distribution and their characteristics in a fixed bed reactor. The solid products (torrefied EFB) obtained were analyzed by various methods such as proximate and ultimate analyses, CV, scanning electron microscopy (SEM), Fourier transform infrared (FTIR), x-ray diffraction (XRD) and thermogravimetric analysis (TGA) and chlorine content. Meanwhile, the liquid product was characterized for chemical compositions via gas chromatography-mass spectrometry (GC-MS), CV, water content, pH and elemental compositions while the gas product for gas types and distribution. Optimum temperature to produce torrefied EFB was identified at 225 ºC, while optimum residence time and particle size were 20 min and 500-700 µm, respectively for a maximum mass and energy yields. It was found that the torrefaction temperature had the greatest influence on mass and energy yields of torrefied EFB compared to residence time and particle size. The resulted torrefied EFB experienced changes in fuel and structural properties including mass reduction, rise in energy content and chemical compositions. While volatile matter (44%), chlorine (54%) and oxygen contents (37%) of the torrefied EFB were reduced inevitably, fixed carbon (274%), carbon content (45%) and CV (46%) were enhanced. Oxygen removal from EFB during torrefaction migrated to the liquid and gaseous products, most dominant as water and CO2, followed by CO and oxygen-containing organic compounds. The liquid product consisted of condensable components; water (main) and functionalised compounds, among which were acids (as relatively higher concentration), furans, ketones, alcohols and phenols. The gaseous product was dominated by CO2 and CO in all torrefaction conditions. In addition, the potential energy recovery from torrefied EFB at different moisture content of feedstock were determined, and their potential to replace palm kernel shell as boiler fuel was assessed. Empirical equations generated by the developed model were accurate and can obtain a satisfactory fit to the experimental data, with coefficient of determination values higher than 0.96.

Comments

Thesis (PhD) - Faculty of Engineering, Universiti Malaya, 2022.

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