Development and characterisation of continuous fast pyrolysis of oil palm shell for bio-oil production

Abstract

Fast pyrolysis of biomass is the most promising technology of converting solid biomass to liquid bio-oil as a renewable substitution of fossil resources in fuel and chemical feedstocks applications. Malaysia with abundant biomass resources especially from palm oil milling industry provides an ideal platform for the development of this thermal conversion technology. This study was aimed of developing a 6.0 kg/h pilot scale continuous fast pyrolysis system with oil palm shell (OPS) as the main feedstock. A two-stage fluidised bed reactor was designed based on the fluidisation technology with silica sand as the heat carrier to achieve rapid heat transfer required for the reaction. The amount of silica sand required was determined with the experimental study on cold-flow hydrodynamics and heat transfer performances. This reactor can be rapidly heated up from room temperatures to experimental conditions up to 500 oC within 15 minutes. The experimental study of OPS fast pyrolysis showed that the reaction temperature was the most dominant parameter to influence the process sustainability and bio-oil yields. Smooth process and substantial bio-oil yields could be achieved for the experiments carried out with the reaction temperature within 370 oC to 490 oC. Lower reaction temperature will result in inadequate heat to crack the biomass component while the higher reaction temperature will promote secondary reaction to produce more non-condensable gas than bio-oil. The maximum bio-oils yield up to 43.3 wt% was recorded at the reaction temperature of 430 oC by using moderate particle sizes within 212-600 µm in dry basis. The bio-oil produced was dark brown mobile liquid with the physical properties similar to heavy oil. From the analysis of Gas Chromatography - Mass Spectrometry (GCMS), the OPS bio-oil comprising mainly phenolic compounds, carboxylic acids and aldehydes. The bio-oil can be used for the manufacturing of phenolic resin or further upgraded for liquid fuel production. The development of fast pyrolysis system for oil palm solid wastes exhibits great potential to bring positive impact to Malaysia palm oil industry as it can broaden the industry’s products spectrum and generate revenue from these wastes.