Simulation of biomass-plastic co-gasification in a fluidized bed reactor using Aspen plus

A detailed process model was developed for co-gasification of biomass and plastics in a fluidized bed reactor using Aspen Plus with kinetic-based reactors. Governing kinetic expressions were adopted from the literature and nested in the Aspen Plus software to carry out the simulation. This study involves steam co-gasification of sawdust with Polyethylene (PE) and Polypropylene (PP). It is aimed at determining the synergistic effects of mixing PE and PP (0-30%) with lignocellulosic biomass on the syngas composition, hydrogen to carbon monoxide ratio (H2/CO), and higher heating value (HHV). Effects of process parameters including the reactor temperature, steam/feedstock ratio (S/F), plastic content and pressure are also discussed. Increase in plastic content leads to higher hydrogen concentration in the syngas resulting from primary and secondary reforming reactions. Highest hydrogen concentrations of 65.32% and 63.80% were obtained respectively for PE-biomass and PP-biomass gasification at 30% plastic content and 750 degrees C. Reduction in CO was obtained due to the decrease in oxygen content in the feedstock with increase in plastic content and consequently leads to increase in H2/CO. Increased hydrogen content and syngas with higher HHV is achieved as the gasification temperature was increased. Hydrogen content was increased to a maximum of 61.99% and 60.57% at 800 degrees C for PE and PP cogasification, respectively.