Numerical investigation of the effects on polypropylene combustion by the addition of water vapour and CO₂ to high temperature oxidizer

To investigate the combustion mechanism of polypropylene (PP), which is a major waste polymer, polypropylene combustion in a high temperature oxidizer was investigated numerically using a counterflow configuration. Detailed chemical kinetics in the gas phase, the overall reaction in the condensed phase, and the gas and surface radiation were taken into account. The regression rates were calculated using two kinds of radiation models, the optically thin model (OTM), which neglects the effect of radiation reabsorption, and the statistical narrow band model (SNB), which considers radiation reabsorption and wavelength dependence of radiating gaseous species. The results show that not only a highly preheated oxidizer but also a high mass flow rate of oxidizer is needed to increase regression rates and that extinction limits can be broadened by a highly preheated oxidizer. The H₂O enrichment was found to be more effective than that of CO₂ to increase the regression rate, because the effect of radiation reabsorption is significant in the case of CO ₂ enrichment and leads to a decrease in gas radiation to PP. Therefore, it is considered that, in the case of high dilution with combustion product gas, OTM can no longer be employed.