Co-gasification of plastics waste and biomass in a pilot scale fluidized bed reactor

Co-gasification tests were carried out in a pilot scale bubbling fluidized bed gasifier, large enough to exclude any scale-up effect, and able to treat up to 100 kg/h of plastics and biomass mixtures. It was operated under chemical and thermal steady-state, with equivalence ratios varying from 0.19 to 0.28, and plastics/biomass blending ratios from mono gasification of plastics to that of biomass. The results are reported in terms of main process performance parameters and axial profiles of syngas composition and reactor temperature. They indicate that plastics/biomass ratio and equivalence ratio remarkably affect the gasifier performances, even though the obtained syngas was always of rather good quality, with a low heating value between 7 and 10 MJ/m3N. The axial syngas compositions showed a monotonic reduction of carbon dioxide concentration (of about 20–30%) and a corresponding increase of hydrogen concentration (of about 90–110%), highlighting the key role of water gas shift, and steam and dry reforming reactions. The overall set of results provides information about the feasibility of co-gasification of plastics waste and biomass at a demonstration scale and supports the optimisation of design or operating criteria as well as the implementation of reliable numerical models of bubbling fluidized bed gasifiers.