Effect of Co-firing Rate on Dewatered Sludge and Municipal Solid Waste Incineration: Pollutants Emissions, Operational Performance and Byproducts

• • At a 5% sludge co-firing rate, fan flow rate decreased by 24.0%, fan power consumption dropped by 56%, ammonia consumption reduced by 31.4%, and lime consumption by 24.7%, while steam production fell by 15.1% compared to 0% co-firing, indicating a trade-off between operational efficiency and energy recovery. • • Increasing the co-firing rate from 5% to 10% degraded combustion conditions, leading to higher flue gas volume, fan flow, and reagent consumption, and further reduced steam production from 2.358 t/t to 2.117 t/t, demonstrating a non-linear penalty on system efficiency. • • Fly ash leaching toxicity tests showed that Zn leached concentration dropped from 31.325 mg/L at 0% co-firing to 2.513 mg/L at 5% and 0.876 mg/L at 10%, while Pb decreased from 0.05 mg/L to 0.03 mg/L and below detection at 10%, all well below GB 16889—2008 limits, confirming effective stabilization. • • Hg, As, Ba, and Se leached concentrations increased with co-firing rate (e.g., Hg from 2.61×10⁻⁴ to 3.88×10⁻³ mg/L; As from 2.23×10⁻³ to 0.14 mg/L), yet remained far below regulatory thresholds, indicating that sludge co-firing alters heavy metal speciation but does not compromise landfill disposal compliance.