Gasification-MILD combustion technology with ash-sludge recirculation for reducing multi-phase net dioxin discharges...

This study addresses the challenge of reducing "net" toxic pollutant discharge, specifically dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), while minimizing the energy consumption and costs associated with detoxification. Our research focuses on reintroducing fly ash and scrubber sludge (ASR) into a hazardous waste thermal treatment system equipped with gasification-intense low oxygen dilution (GASMILD) and an advanced air pollution control system (APCS). This approach yielded a remarkable PCDD/F removal efficiency exceeding 99.9% for both mass and toxic equivalent (TEQ), achieving a net destruction of PCDD/Fs within the system. The success can be attributed to the ASR material's richness in ultrafine particles, which act as nucleation cores during combustion, promoting particle growth and enhancing the capture of PCDD/Fs in the APCS. This leads to a significant reduction (over 93%) in both PCDD/F mass and World Health Organization-toxic equivalent (WHO-TEQ) concentration in the flue gas. While a phase transition of gaseous PCDD/Fs within the APCS caused a shift in the particle size distribution towards larger particles, the overall PCDD/F mass concentration in the stack emissions remained lower with ASR. Notably, the reintroduced PCDD/Fs tend to deposit in the nasal region of the respiratory tract, potentially reducing the health risks associated with deeper lung deposition. This research demonstrates the effectiveness of ASR in achieving net PCDD/F destruction within a GASMILD combustion system, offering a promising strategy for cleaner and more sustainable waste management practices. From a managerial perspective, this approach provides a cost-effective solution for PCDD/F mitigation, contributing to reduced emissions and improved public health.