Properties of composite sintered modified fluidized bed incineration fly ash as cement admixture

As a hazardous solid waste, circulating fluidized bed incineration fly ash faces the risk of heavy metal leaching and excess dioxin content, and thermal treatment plays an important and increasingly evident role in its environmentally sound disposal. This paper summarizes numerous studies and proposes the composite sintering of circulating fluidized bed incineration fly ash with limestone powder. The operation of the composite sintering on the physicochemical properties of circulating fluidized bed incineration fly ash and the performance of the cement prepared as cement admixture were studied. The results show that the composite sintering can decompose more than 92.7% of chlorine and 99.9% of dioxins, increase the activity of volcanic ash to 79%, and produce new minerals - Ye'elimite and Larnite, However, the content of heavy metals will increase due to the enrichment. The prepared cement can solve the bulk cracking caused by aluminum, reduce the water demand by more than 3.6%, and increase the 3 d compressive strength by 19.09% at 5% admixture and 50.2 MPa at 28 d. Besides, there is no risk of excessive leaching of heavy metals. The content of fly ash from circulating fluidized bed incineration in cement increases from 0.52% to 7.14% after composite sintering. It is proved that composite sintering is beneficial to the enhancement of the resource recovery capacity of hazardous solid waste in the cement industry. In this experiment, chlorine remains the most critical factor limiting its application, and the removal of chlorine should be the focus of the subsequent experiments to expand its resource recovery pathway.