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Improvement of bio-crude oil properties via co-pyrolysis of pine sawdust and waste polystyrene foam

Van Nguyen, Quynh, Choi, Yeon Seok, Choi, Sang Kyu, Jeong, Yeon Woo, Kwon, Yong Su
Journal of environmental management 2019 v.237 pp. 24-29
acetic acid, biofuels, biomass, commercialization, fluidized beds, foams, fossil fuels, fuel oils, liquids, mixing ratio, nitrogen, plastics, polystyrenes, pyrolysis, sawdust, synergism, temperature, thermogravimetry, viscosity, wastes, water content
Conversion technology of solid biomass to liquid fuel, named bio-crude oil, has been researched widely for the production of renewable energy to replace fossil fuel oil. As the result of many admirable researches, fast pyrolysis technology for bio-crude oil production is close to commercialization. However, bio-crude oil has unsatisfactory properties compared to general petroleum oil, for instance, low heating value, high water content, and high viscosity. In this study, pine sawdust (SD) biomass was co-pyrolyzed with waste polystyrene foam (WPSF), which was expected to improve the bio-crude oil quality due to high heating value and non-oxygen composition of polystyrene. The co-pyrolysis experiment was conducted in a bubbling fluidized bed reactor under the following conditions: temperature of 500 °C which was chosen based on the results from thermogravimetric analysis of SD and WPSF, nitrogen flow rate of 20–25 L/min., and feeding rate of 200 g/hr. Various mixing ratios of SD/WPSF by weight percentage were tested as follows: 100/0, 95/5, 90/10, 85/15, 80/20, 75/25, 70/30, 60/40, 50/50, 25/75, 0/100. Experimental results showed that in case of only SD feeding the bio-crude oil yield and higher heating value (HHV) were 48.83 wt% and 17.81 MJ/kg respectively. By contrast, oil yield and HHV in case of 25% SD with 75% WPSF mixture were 63.31 wt% and 39.65 MJ/kg respectively. Additional analysis showed that water content, and acetic acid concentration of bio-crude oil from co-pyrolysis of SD/WPSF mixture were decreased almost proportionally with the increasing WPSF ratio. Furthermore, measured values of water content, and acetic acid concentration were lower than the calculated values by linear interpolation, which means that the synergistic effect between SD and WPSF was achieved during the co-pyrolysis. In conclusion, co-pyrolysis of SD and WPSF was found as a promising solution to improve bio-crude oil quality. With this technology, the industrial growth of bio-crude oil area is expected as well as waste plastic.