A novel and clean utilization of flue gas desulfurization ash coupled with converter sludge to produce calcium ferrate

[Display omitted] •An innovative method to prepare calcium ferrate was proposed from desulfurization ash.•Thermogravimetric and infrared techniques were used to study gas formation.•The new process effectively removes sulfur and alkali heavy metals.•This technology provides a sustainable solution for utilizing converter sludge. To address the environmental pollution from industrial wastes like desulfurization ash (DA) and converter sludge(CS), this study introduces a novel method for synthesizing calcium ferrate. This method involves reacting converter sludge with desulfurization ash at high temperatures, facilitating the concurrent elimination of toxic elements. The solid byproduct is suitable as a sintered ore additive, while the gaseous SO2 serves as a precursor for sulfuric acid production. Additionally, the metal-rich secondary dust offers a source for valuable metal recovery. This research employs simulation software (FactSage 8.1) and thermal analysis to explore the high-temperature reaction dynamics of converter sludge and desulfurization ash. Subsequent in-situ experiments and coupled high-temperature tube furnace-infrared flue gas analysis further elucidated the phase transitions, morphology changes, flue gas emissions, and migration of harmful elements (e.g., S, K, Na, Pb, Zn). Analysis using the Predom dominant zone module calculation indicates that low SO2 concentration and reduced oxygen levels promote the stability of Ca2Fe2O5. Infrared flue gas analysis reveals high concentrations of CO2 and SO2. Sulfur removal rates rose from 62.15 % to 98.48 % between 800 °C and 1100 °C. Removal efficiencies for alkali and heavy metals, namely K, Na, Pb, and Zn, improved significantly, reaching 99.95 %, 99.49 %, 99.71 %, and 86.7 % respectively. At 1100 °C under an N2 atmosphere, the main reaction products from Flue Gas desulfurization ash (FGDA) and converter sludge were CaFe3O5 and Ca2Fe2O5. This study’s comprehensive analysis of synthesizing calcium ferrate from Flue Gas desulfurization ash and converter sludge introduces a novel waste utilization method, offering substantial environmental and economic advantages.