Sustainability, Vol. 10, Pages 4854: Utilization of CFBC Fly Ash as a Binder to Produce In-Furnace Desulfurization Sorbent (Sustainability)

Circulating fluidized bed combustion (CFBC) power generation technology is known to efficiently reduce the emission of air pollutants, such as SO2 and NO2, from coal combustion. however, CFBC coal ash contains high contents of free CaO, making it difficult to recycle. This research has been conducted to find ways to use the self-hardening property of CFBC coal ash, one of its inherent characteristics. As part of these efforts, the present study intended to investigate the properties and desulfurization efficiency of Ca-based desulfurization sorbents using CFBC fly-ash as a binder. Limestone powder was mixed with CFBC fly-ash and Ca(OH)2 to fabricate desulfurization sorbents, and it generated hydrate of cement, including portlandite, ettringite, and calcium silicate, etc. The compressive strength of the desulfurization absorbent prepared by CFBC fly ash and Ca(OH)2 was 72–92% that of the desulfurized absorbent prepared by using general cement as a binder. These absorbents were then compared in terms of desulfurization efficiency using a high-temperature fluidized bed reactor. It was confirmed that the desulfurization absorbents fabricated using CFBC fly-ash as a binder achieved the best performance in terms of absorption time, which reflects the time taken for them to remove over 90% of high-concentration SO2 gas, and the conversion ratio, which refers to the ratio of CaO turning into CaSO4.