Numerical modeling of plasma gasification process of polychlorinated biphenyl wastes

Abstract

The plasma gasification process is one of the most innovative and efficient methods for the disposal of various wastes and energy production. But it is still an extremely complicated process; therefore, to optimize it, modeling could be used as an invaluable asset. The aim of this study is to develop a computational model to evaluate the plasma gasification process of polychlorinated biphenyl wastes. The model was created in Aspen Plus® commercial software. It is based on the principle of Gibbs free energy minimization. The results acquired in this research were validated by the data in the literature. It has to be noted that satisfactory results have been obtained. Also, air, steam, and carbon dioxide were considered as oxidizers and the effects of various parameters such as temperature, equivalence ratio (ER), steam-to-waste (S/W) ratio, and carbon dioxide-to-waste (CO2/W) ratio on the production of syngas components were investigated. The results show that processing this hazardous waste leads to the production of a large percentage of acidic gases, which demands a gas cleaning unit in such treatment facilities. The results also show that PCBs with lower chlorine atoms are favorable to the production of higher-quality syngas. The increase of the gasifier temperature turns the waste into purer syngas. However, after the temperature of 1200 oC the results showed that the major constituents of syngas reach almost a constant molar fraction. A steam-to-waste ratio of 0.5 can be used to produce syngas with greater percentage of hydrogen and fewer pollutants. The use of CO2 as gasifying agent led to the production of large amounts of CO. Conclusion could be drawn that this process can be considered safe and very effective while processing the aforementioned hazardous wastes and in the production of high-quality syngas.