Abstract
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.
Highlights
As one of the clean coal technologies (CCTs), circulating fluidized bed combustion (CFBC) technology is being widely used as a solution for eco-friendly power generation thanks to its ability to effectively control the emission of sulfur oxides and nitrogen oxide generated by coal-fired power plants [1,2]
A CFBC power plant is equipped with a boiler whose inside temperate reaches 850–900 ◦C, which allows it to generate less sulfur oxide and nitrogen oxide emissions than pulverized coal combustion (PC) power plants
Coal ash generated from CFBC power plants contains high contents of free CaO and CaSO4, which is generated from the limestone inserted to promote in-furnace desulfurization
Summary
As one of the clean coal technologies (CCTs), circulating fluidized bed combustion (CFBC) technology is being widely used as a solution for eco-friendly power generation thanks to its ability to effectively control the emission of sulfur oxides and nitrogen oxide generated by coal-fired power plants [1,2]. The present study aimed to promote the utility of CFA, one type of CFBC coal ash, by devising methods to use it as a raw material in binders added to fabricate CFBC desulfurization sorbents, which can be reused in the power generation industry. This intended approach is a step forward, beyond its typical use of replacing cement as a binder. These Ca-based desulfurization sorbents were tested under high-temperature fluidized bed reaction conditions, and compared with respect to their SO2 absorption time and the corresponding conversion ratio
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