Plastic pollution has become an enormous challenge for human beings and the environment due to its widespread use and low degradation. The treatment of plastic waste by gasification technology has attracted more and more attention. However, the syngas evolution and energy recovery of the plastic mixture during CO₂-assisted co-gasification are less studied. The co-gasification of the polypropylene (PP) and polystyrene (PS) blends at different proportions was carried out in a fixed-fed reactor at 1173K. The gas flow rate, yield, and recovered energy of gaseous products were quantitatively investigated. The experimental results of CO, H₂, hydrocarbon (C_xH_y) yields and energy output in comparison with weighted results from the gasification of individual compositions indicated that co-gasification had positive effects on the yield and energy output. The maximum synergistic effects on CO and H₂ yields were obtained under a 2:3 mixing ratio of PP/PS (2P3S), and the synergistic effects of energy output also reached the optimum level. However, the synergistic effects in the whole gasification process gradually weaken as the PP ratio increases. Total syngas with a calorific value of 24.2-28.4 kJ/g was generated through CO₂-assisted co-gasification, which was much larger than the energy output of individual feedstocks. And the syngas with the highest energy output of 28.4 kJ/g had CO and H₂ mole fractions of 93.4% and 1.5% under a 2P3S mixing ratio, respectively. The CO₂ consumption belonged to each gram of these blends was a range of 1.0-1.8g in the process. These results support the feasibility of converting plastic mixture to high calorific value syngas through CO₂-assisted gasification and reducing the greenhouse effect by consuming CO₂.
 

synergistic effects, polypropylene, polystyrene, energy recovery, CO2 consumption