Combination of Light Bio-oil Washing and Torrefaction Pretreatment of Rice Husk: Its Effects on Physicochemical Characteristics and Fast Pyrolysis Behavior

A combination of light bio-oil washing and torrefaction pretreatment of rice husk samples was proposed in this study, to investigate the impact on physicochemical characteristics and fast pyrolysis behavior. The results indicated that pretreatment removed a significant percentage of metallic species and significantly improved the fuel characteristics of rice husk samples. Fourier transform infrared spectroscopy (FTIR) analysis indicated that some organic groups decomposed by dehydration and decarboxylation reactions during the process of torrefaction pretreatment. The results of fast pyrolysis indicated that the yield and quality of pyrolysis products significantly changed with combined light bio-oil washing and torrefaction pretreatment. Pretreatment resulted in a significant increase of pH and higher heating values (HHVs) along with a reduction of the water content. Meanwhile, it can be obtained from gas chromatography/mass spectrometry (GC/MS) analysis of bio-oil that pretreatment enhanced selective pyrolysis toward production of sugars, especially levoglucosan. In view of the developed pore structure and high silica content of char obtained from fast pyrolysis of rice husk with a combination of light bio-oil washing and torrefaction pretreatment, this char can be used as the resource to produce activated carbons and amorphous silica.