Syngas Quality Enhancement by CO2 Injection during the Co-Gasification of Biomass and Plastic

Gasification technologies have been considered to be viable waste enhancement avenues for diverting mixed nonrecycled plastic-containing waste from landfills. The main objective of this work was to investigate CO2 utilization with the air gasification of mixed plastics and biomass. High-density polyethylene (HDPE) was co-gasified with Douglas fir, air, and CO2 in a semibatch updraft gasifier with supporting thermogravimetric analyzer (TGA) testing. Possible reaction mechanisms of the mixed feedstock with CO2 injections were discussed by comparing the gas, tar, and char products of the gasifier with the TGA data. Injecting 10 and 20 vol % CO2 in air gasification with an air to fuel ratio of 0.3 improved carbon conversion from the tar to the gas phase by 28 and 43 carbon weight %, respectively. CO2 addition was an effective moderator of the H2/CO ratio, beneficial to tar reduction and enhanced the energy density of the syngas, improving the tunability of the gasification process.