Co-pyrolysis of Sawdust and Rice Husk in a Fluidized Bed Reactor: Yields and Properties of Products with Techno- economic Analysis / Nur Amal Fadhilah binti Narawi

submitted in fulfilment of the requirements for the degree of Doctor of Philosophy

Abstract

Brunei Darussalam is one of the countries that completely depends on fossil fuels for its energy demand. The country should take advantage of utilizing its biomass solid waste as an alternative energy source. Pyrolysis is one of emerging technology to derive bio- fuels from biomass solid waste. In this study, co-pyrolysis technique was employed to improve the yield and properties of bio-fuels which also could help solid waste management in Brunei Darussalam. From feedstock characterization study, sawdust and rice husk were selected as the feedstock mixture. The blending ratio of sawdust to rice husk was varied between 0:100, 75:25, 50:50, 25:75 and 100:0 with 0.1 kg/h feed throughput. The co-pyrolysis system has been designed and fabricated consisting of the fluidized bed reactor, heating cylinder, cyclone, condenser and liquid collector. An experimental study was performed using sand as the reactor bed particles and nitrogen gas as the fluidizing gas. Parameter variations are temperature and nitrogen gas flow rate. The optimal temperature observed was 500°C with a maximum bio-oil yield of 54.3% at blending ratio of 100:0. Meanwhile, the optimal nitrogen gas flow rate was 20 L/min with a maximum bio-oil yield of 51.9% at blending ratio of 50:50. There was a synergetic effect observed with the addition of sawdust, as the yield of bio-oil obtained are higher than the calculated value. In addition, the oxygen, sulphur and nitrogen content in bio-oil and bio-char is also reduced. This results in the increase of the gross calorific value with a maximum of 23.56 MJ/kg and 26.91 MJ/kg for bio-oil and bio-char respectively. From Fourier Transform Infra-red (FTIR) spectroscopy analysis, phenols and aromatic compounds were detected in bio-oil and bio-char. Techno-economic analysis found that a plant capacity of 1000 kg/h is the most economically viable option with minimum unit production cost of 0.071 BND/kg for bio-oil and 0.12 BND/kg for bio-char at a blending ratio of 50:50 and 100:0, respectively. From the mass and energy balance, by increasing the plant capacity, there was a significant increase in thermal efficiency of 63.5% at a plant capacity of 1000 kg/h. This study has proven the blending of sawdust and rice husk does help to enhance the bio-oil yields and properties of bio-fuels compared to pyrolysis of the rice husk alone. Additionally, larger plant capacity of the co-pyrolysis system is recommended for its commercialization. The bio-fuel obtained has potential to be used as a conventional fuel substitute or as value-added chemicals.

Dissertation (Master) - Universiti Teknologi Brunei

Included bibliographical references