Fast pyrolysis of biomass and waste plastic in a fluidized bed reactor

• A mixture of red oak and HDPE is fast pyrolyzed in a fluidized bed.
• Optimum pyrolysis temperature was 625 °C.
• A significant synergistic effect between red oak and HDPE was found.
• Co-pyrolysis reduces char formation from red oak.
• Pyrolysis char had a lower BET surface area than red oak biochar.

Co-pyrolysis of red oak and high density polyethylene (HDPE) was conducted in a laboratory-scale, continuous fluidized bed reactor in a temperature range from 525 to 675 °C. Pyrolysis products, including two fractions of pyrolysis-oil, non-condensable gases and char were analyzed to assess the influence of pyrolysis temperature and co-feeding of biomass with HDPE. It was found that increasing pyrolysis temperature up to 625 °C promoted the production of pyrolysis-oil and its yield reached 57.6 wt%. Further increase in pyrolysis temperature caused the cracking of pyrolysis-oil to form light gases rich in hydrocarbons. Organic phase of pyrolysis-oil produced from plastic-biomass mixture (PBM) had a higher heating value (HHV) up to 36.6 MJ/kg contributed by the additive effect of HDPE-derived aliphatic hydrocarbons. A significant synergetic effect was also observed during co-pyrolysis. Co-pyrolysis with HDPE increased the production of furan, acids and water from red oak. Co-presence of HDPE also inhibited char formation from red oak and improved the HHV of the resulting char. The char produced from co-pyrolysis had a significantly lower BET surface area than red oak biochar. Not only did HDPE-derived particulate matter blocks the pores, the synergetic interaction also resulted in the formation of large and shallow micro-pores on the char surface.