Fast pyrolysis of wheat straw in a dual concentric rotary cylinder reactor with ceramic balls as recirculated heat carrier

Fast pyrolysis of wheat straw in an original dual concentric rotary cylinder (DCRC) reactor with ceramic balls as recirculated heat carriers was studied to access the performance of this unit and explore the product yields and and characteristics in response to temperature. In addition, the performance of the novel bio-oil recovery mode (NBRM) was evaluated and compared with the spray quenching mode. Detailed composition of the bio-oils obtained under optimal conditions by using the NBRM was also analyzed. The DCRC reactor along with the novel bio-oil recovery procedure was successfully scaled up to a 25 kg/h pilot plant and showed good performance. The bio-oil yield was elevated by 21.4% when raising temperature from 400 to 500 °C with the peak value of 47.6 wt%. The prevailing components of pyrolysis gas are CO2 and CO, both of which account for at least 75 vol%, with the lower heating values increasing from 6.2 MJ/m3 at 400 °C to 13.6 MJ/m3 at 700 °C. Compared to the spray quenching way, the bio-oil yields were always elevated at different temperatures when using the NBRM and the increase rate showed an unceasing increase from 2.8% at 400 °C to 9.6% at 700 °C, which confirmed the better performance of NBRM in response to more pyrolysis vapors generated at higher temperatures. The obtained results provided valuable insights into the fundamentals of biomass pyrolysis in the DCRC reactor, as well as the scale-up and technology breakthrough of the originally developed unit.