Hydrothermal liquefaction of oil mill wastewater for bio-oil production in subcritical conditions

The main purpose of this study is to investigate the direct hydrothermal liquefaction of oil mill wastewater (OMWW). Experiments were carried out at different temperatures (240-300°C), water contents (58-88wt.%) and reaction times (15-45min). Results show that the highest bio-oil yield was about 58wt.%, resulting in a higher heating value of 38MJ/kg. This was conducted at the following optimal conditions: water content 88wt.%, a temperature of 280°C, and 30min as reaction time. To put bio-oil into wide application, the various physical and chemical characteristics were determined. A detailed chemical composition analysis of bio-oil was performed by gas chromatography-mass spectrometry (GC-MS) coupled with a flame ionization detector (FID). The dominant compounds were identified by using NIST library. Analyses show that the bio-oil contains mainly oleic acid, hexadecanoic acid, fatty acid methyl ester, fatty acid ethyl ester, amino acid derived compounds and phenolic compounds.