Thermal pyrolysis of linseed waste to produce a renewable biofuel using response surface methodology in a fixed bed reactor

Abstract

Declining fossil fuel reserves, pollution and their destructive impact on the environment have led researchers to turn to alternative energy sources. The importance of using alternative energy sources to provide transportation fuel in adverse environmental conditions will lead to a growing trend in the production of biofuels, including bio-oils from pyrolysis of non-edible biomass in the world. The aim of this study was to investigate the effect of three variables, i.e. final temperature, biomass particle size and nitrogen flow rate on the yield of products resulting from pyrolysis of linseed waste. The final temperature, nitrogen gas flow rate and particle size (based on mesh number) were selected in the range of 320–580 °C, 0–250 cm3/min and 150–600 µm (mesh no. 30–100), respectively. During the pyrolysis process, linseed waste was converted into solid, liquid and gas products in a fixed bed reactor with a constant heating rate of 20 °C/min. Maximum bio-oil yield was obtained at 550 °C, biomass particle size of 150 µm and flow rate of 200 cm3/min, 55.879 wt%. Liquid and solid products were analyzed by GC/MS, FTIR and SEM analyzes. Based on the results of GC/MS experiments performed on the samples of this study, 56, 60, 66 and 62 compounds were identified at temperatures of 320, 450, 550 and 580 °C in the structure of biofuels from linseed waste, respectively. Bio-oils mainly had C2-C31 hydrocarbon range. On the other hand, the obtained properties of bio-oils are comparable to petroleum diesel and biodiesel. Therefore, the bio-oil produced can be used both as a hydrocarbon fuel and as a chemical. FTIR analysis also shows the presence of functional groups such as phenols, alcohols, aromatic compounds, alkanes and its subunits, ketones, carboxylic acids and others. The results of GC/MS and FTIR analyzes support each other. Pyrolysis bio-char can also be used as a solid fuel.