REDUCTION OF DIOXIN EMISSION BY MULTI-LAYER MOVING BED REACTOR WITH BEAD-SHAPED ACTIVATED CARBON

In this study, a dioxin-containing gas stream generating system was developed to investigate the efficiency and effectiveness of newly developed polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) control technology. The system constructed can stably generate the gas stream with the PCDD/F concentration ranging from 1.0 to 1,000 ng-TEQ Nm -3 (toxic equivalence, TEQ). In addition, we also develop a laboratory-scale multi-layer moving bed reactor for PCDD/F adsorption at various operating conditions, including gas flow rate, operating temperature and water vapor content. Excellent PCDD/F removal efficiency (> 99.99%) was achieved with the multi-layer adsorber with bead-shaped activated carbons (BACs) as adsorbent. The PCDD/F removal efficiency with first layer adsorption bed decreased as the gas flow rate increased. This is attributed to the fact that as gas stream passes through a constant sectional area, the gas velocity increases with the increase of the gas flow rate, causing the decrease of the retention time. The PCDD/F concentrations measured at the outlet of third layer adsorption bed are all lower than 0.1 ng-TEQ Nm -3 . In this study, water vapor was found to significantly affect the distribution of PCDD/F congeners. The PCDD/Fs desorbed from BACs were mainly lowly chlorinated congeners and the PCDD/F outlet concentrations increased with increased operating temperature.