Advances on resource utilization of semi-dry desulfurization ash by thermal decomposition: a high-efficiency and...

The semi-dry flue gas desulfurization ash (SFGDA) is an industrial waste generated by the semi-dry desulfurization process, and its resources have been continuously attracted attention. Through the method of heat decomposition, the SFGDA decomposed into CaO and SO₂ has emerged as a prominent research topic. This paper summarizes various of research workers, who revealed that the decomposition temperature of CaSO₄ in SFGDA is greater than 1678 K and 1603 K in the air atmosphere and N₂ atmosphere, respectively, presenting challenges such as high energy consumption and limited economic feasibility. On the one hand, the effects of CO and C regulating the pyrolysis atmosphere on reducing the pyrolysis temperature were reviewed. On the other hand, the impact of additives such as Fe₂O₃ and FeS₂ was considered. Ultimately, the joint effects of regulating atmosphere and additives were discussed, and an efficient and low-temperature decomposition route was obtained; adding solid C source and Fe₂O₃ for pyrolysis reaction, the decomposition temperature of CaSO₄ can be reduced by at least 230 K and desulfurization efficiency exceeds 95% under the condition of micro-oxidizing atmosphere. Moreover, the CaO resulting from SFGDA decomposition can be further synthesized into calcium ferrite, while the enriched SO₂ can be utilized for the production of industrial sulfuric acid, which holds promising prospects for large-scale industrial applications.