Distribution Characteristics of Valuable Elements, Al, Li, and Ga, and Rare Earth Elements in Feed Coal, Fly Ash, and Bottom Ash from a 300 MW Circulating Fluidized Bed Boiler

Zhibin Ma; Xueyuan Shan; Fangqin Cheng

doi:10.1021/acsomega.9b00280

Distribution Characteristics of Valuable Elements, Al, Li, and Ga, and Rare Earth Elements in Feed Coal, Fly Ash, and Bottom Ash from a 300 MW Circulating Fluidized Bed Boiler

ACS Omega. 2019 Apr 16;4(4):6854-6863. doi: 10.1021/acsomega.9b00280. eCollection 2019 Apr 30.

Authors

Zhibin Ma^{1

1

2}, Xueyuan Shan^{1

1}, Fangqin Cheng^{1

1}

Affiliations

¹ State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources, Institute of Resources and Environmental Engineering and Collaborative Innovation Center of High Value-added Utilization of Coal-related Wastes, Shanxi University, Taiyuan 030006, P. R. China.
² Centre for Energy, The University of Western Australia, Crawley 6009, Australia.

Abstract

Feed coal, fly ash (FA), and bottom ash (BA) were collected from a 300 MW circulating fluidized bed boiler. A mechanical screen classifier was used to separate and obtain particles with different sizes. The distribution of valuable elements, including aluminum (Al), lithium (Li), and gallium (Ga), and rare earth elements (REE) in the samples was investigated. Results indicate that the contents of SiO₂ and Al₂O₃ in sized ash particles decreased as the particle size decreased; meanwhile, the contents of CaO, SO₃, and Fe₂O₃ apparently increased. The sulfur-fixing product anhydrite tended to be distributed in the fine ash particles. The valuable elements were more enriched in FA than in BA. The Li, Ga, and REE were evenly distributed in FA particles with different sizes. Separating ash particles with a superhigh concentration of these rare elements was difficult using the mechanical screen, but a part of the anhydrite or CaO in circulating fluidized bed ash could be removed easily. The Li and REE in the feed coal were highly associated with quartz, kaolinite, and other fractions containing SiO₂ and Al₂O₃. No definitive relationship between the Ga concentration and Al₂O₃ content in the feed coal and ash samples was observed.