Improvement of a biomass pyrolysis system for bio-fuels / Siti Muslihah binti Haji Masri

A thesis submitted to the Universiti Teknologi Brunei (UTB) in partial fulfillment of the requirements for the degree of Master of Science (MSc) in Mechanical Engineering

ABSTRACT
Pyrolysis is the conversion of ligno-cellulosic biomass to bio-fuel. Bio-fuel extracted is divided into three categories, bio-oil, bio-char and non-condensable gas. In this research, Napier grass and Laila paddy rice husk were collected locally, processed, dried and pyrolysed in an inert condition with nitrogen gas with flow rate of 10L/min and running time of 45 minutes. An existing biomass pyrolysis unit has been designed and tested where the system includes a fixed bed reactor connected to a parallel flow pipe design condenser for direct heat exchange. The first improvement include a combination of gas heating and biomass heating were used. Local sawdust was used as heating source for the heating system and Liquid Petroleum Gas (LPG) for the gas heating system with a weight ratio of 6:1. Coarse and fine sawdust were used as the biomass heating source with weight ratio of 3:1. Second and third improvements that has been added to the system were a cyclone of 7 cm body diameter according to its optimal dimension ratios, and glass fiber insulation inside the burner that act as a reactor shield. The first part of the study is to determine the influence of pyrolysis temperature (250°C, 350°C, 450°C and 550°C) for the particle size of 0.85 millimeter and the second part of the study is to determine the influence of biomass particle size (0.85 mm, 1 mm and 2mm) under constant temperature of 550°C, and finally, the products were analyzed for their physical and chemical properties. The apparent vapor residence time was estimated at 5 seconds. A maximum of Napier grass bio-oil of 33% by weight dry biomass feedstock was obtained at 550 °C, with heating value of 16.1 MJ/kg and pH of 3.49. The bio-char, at 550 °C, has 40 wt.% product yield, with energy density of 20.5 GJ/m and heating value 35.2 MJ/kg. For rice husk, maximum of 24% by weight dry biomass feedstock was obtained at 550°C, with heating value of 18.6 MJ/kg, and pH of 3.04. The bio-char has 27 wt. % product yield, with energy density of 1.65 GJ/m and heating value 19.1 MJ/kg.
Maximum products have 0.85mm particle sizes.

Dissertation (Master) - Universiti Teknologi Brunei (2018)

Includes bibliographical references and appendices