Investigation of dioxin formation in conventional gasification process with modeled hazardous waste

Abstract

The hazardous waste incineration has significant environmental concern due to its potential to produce dioxin and furan emissions. Thus, the gasification which is a mature technology used to produce energy and chemicals more than 100 years may be used as an alternative to hazardous waste disposal. However, waste gasification has been studied for just decades with refused derived fual (RDF) and municipal solid waste. Therefore, the hazardous waste gasification is completely new research area. The aim of this study was to investigate the applicability of gasification to hazardous waste disposal from the dioxin/furan formation point of view. For this reason, gasification experiments were conducted with modeled hazardous waste which was created by mixing the hazelnut shell and virgin polyvinylchloride (PVC) due to its chlorine content. The factors that effect the dioxin/furan formation were examined and the formation mechanism of dioxins was explained as the result of the research study. The investigation of the results focused mainly on the effect of the operating parameters on dioxin formation and the distribution of dioxin congeners in different sampling points. It was found that the congener distribution in all measurement points showed strong similarity. Whether it was in syngas or in the bottom ash the dominant congeners have similar sequence. This similarity was an indicator that the dioxins were formed from the same macromolecular carbon structure which widely exists as tar form in gasification. Also gasification periods, Equivalence Ratio (ER), temperature and hyrogenchloride (HCl) have direct effect on dioxin formation. The dioxin analysis results also showed that the formation mechanism of dioxins was de novo synthesis which is occurred at the post-combustion zone of the plants in the existing study.