The 6th International Conference on Biomass Energy (ICBE2018)

309 / 2018-08-01 00:00:35

Pyrolyzing agricultural waste by using CO2 for abatement VOCs in biochar

Plenary track > B. Biomass Polygeneration

Biochar contains a large amount of volatile organic pollutants in the pyrolysis production process due to adsorption and pre-condensation of pyrolysis liquid in the pore structure. This paper explores the use of CO2 for pyrolysis to enhance the cracking of volatile organic compounds (VOCs) and reducing the adsorption VOCs in order to reduce VOCs content in biochar. In this study, the pyrolysis experiments of cotton stalk in the atmosphere of N2 and CO2 at 350~750 °C were carried out, using the method of ice water condensation trap / methanol absorption to collect the released organic substances with different condensation characteristics. The released organic substances were classified and detected by GC-MS. The volatile organic compounds in the biochar were detected by SPME/GC-MS, and the pore structure and functional groups of the biochar were detected by BET and FTIR. It was found that BTEx, furan, methyl acetate and other substances mainly exist in the methanol absorption phase. Alcohols, phenols and their derivatives mainly exist in the condensed phase, and acids, furfural and ketones are present in the two. VOCs in biochar mainly include methyl acetate, benzene, undecane, decane, phenols and their derivatives, which are not exactly the same type of the substances released. As the pyrolysis temperature increases, the amount of BTEx release increases, and the content of BTEx in biochar does also increase. At 550 °C, the organic matter in biochar is the most abundant. When it is greater than 650 °C, the main VOCs in biochar is BTEx due to adsorption and the pre-condensation substances become very small. CO2 pyrolysis promotes the cleavage of easily condensable substances, so that the condensable substances in biochar are reduced. At more than 650 °C, the adsorption of BTEx substances with significantly reduced by ~80% compared with the pyrolysis of N2 atmosphere. In general, carbon dioxide pyrolysis can reduce overall adsorption and condensation of VOCs in biochar.