Evolution of deposited carbon during multi-stage fluidized-bed reduction of iron ore fines--颗粒学报PARTICUOLOGY

Du, Z., Zhu, Q., Pan, F., Zou, Z., Xie, Z., & Li, H. (2018). Evolution of deposited carbon during multi-stage fluidized-bed reduction of iron ore fines. Particuology, 41, 11-19. https://doi.org/10.1016/j.partic.2018.03.001

Evolution of deposited carbon during multi-stage fluidized-bed reduction of iron ore fines

Zhan Du ^a, Qingshan Zhu ^{a b *}, Feng Pan ^a, Zheng Zou ^a, Zhaohui Xie ^a, Hongzhong Li ^a

a State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
b University of Chinese Academy of Sciences, Beijing 100049, China

10.1016/j.partic.2018.03.001

Volume 41, December 2018, Pages 11-19

Received 8 December 2017, Revised 27 February 2018, Accepted 4 March 2018, Available online 25 May 2018, Version of Record 1 November 2018.

E-mail: qszhu@ipe.ac.cn

Highlights

• Effects of reduction conditions on carbon deposition of iron ore fines was investigated.

• Addition of H₂ in CO–CO₂ in pre-reduction step promoted the formation of graphite filaments.

• Graphite could inhibit the formation of fibrous iron and decrease the surface viscosity.

• Graphite was more reactive than Fe₃C during gasification and solid-state reduction.

• Carbon deposits acted as efficient reductant for the reduction of FeO to Fe above 950 °C.

Abstract

The influence of reduction conditions on carbon deposition during fluidized-bed pre-reduction of iron ore fines was investigated experimentally. The results showed that reduction temperature and the composition of reducing gases had a significant effect on the rate of carbon deposition and the type of carbon deposits (graphite and Fe₃C). Low reduction temperature, high CO content, and addition of H₂ favored the deposition of carbon, especially graphite. The reduction conditions also significantly affected the surface morphology of the as-reduced iron ore fines. As the amount of deposited graphite increased, the formation of fibrous iron disappeared and graphite filaments were observed. The pre-reduced iron ore fines were further fluidized in pure CO at 850 °C for final reduction. The results showed that graphite could suppress the formation of fibrous iron and decrease the surface viscosity, thereby inhibiting agglomeration during the final high-temperature reduction stage. Reactions that consume the deposited carbon during the final high-temperature reduction were identified and graphite was shown to be more reactive than Fe₃C. To enhance the application of fluidization technology in producing sponge iron, a novel solid-state high-temperature reduction method via deposited carbon was proposed and demonstrated to be feasible.

Graphical abstract

Keywords

Carbon deposition; Multi-stage fluidized-bed reduction; Carbon deposits; Surface morphology

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