Particle mixing behavior of fine coal in density control of gas–solid separation fluidized bed--颗粒学报PARTICUOLOGY

Lv, B., Luo, Z., Fu, Y., Zhang, B., Qin, X., & Zhu, X. (2020). Particle mixing behavior of fine coal in density control of gas–solid separation fluidized bed. Particuology, 50, 76-87. https://doi.org/10.1016/j.partic.2019.07.003

Particle mixing behavior of fine coal in density control of gas–solid separation fluidized bed

Bo Lv ^a, Zhenfu Luo ^{b c *}, Yanhong Fu ^{b c}, Bo Zhang ^{b c}, Xingzong Qin ^{b c}, Xiangnan Zhu ^d

a College of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo 454000, China
b Key Laboratory of Coal Processing and Efficient Utilization of Ministry of Education, China University of Mining & Technology, Xuzhou 221116, China
c School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
d School of Chemical & Environmental Engineering, Shandong University of Science & Technology, Qingdao 266590, China

10.1016/j.partic.2019.07.003

Volume 50, June 2020, Pages 76-87

Received 19 July 2018, Revised 25 June 2019, Accepted 5 July 2019, Available online 4 September 2019, Version of Record 7 April 2020.

E-mail: zfluo@cumt.edu.cn

Highlights

• A variety of particle mixture models were applied to binary mixtures.

• Particle mixing processes were studied with a white magnetite tracer.

• Two-dimensional mixing characteristics of fine coal are explained.

• Bed density was adjusted during the mixing process of fine coal.

• Effects of mixing processes on the separation performance were revealed.

Abstract

In a gas–solid separation fluidized bed, mixing of fine coal is necessary to achieve a suitable bed density to enable effective separation of low rank coal. On the basis of a variety of mixture models, a gas–solid separation fluidized bed was judged, where fine coal particles of 0.6–1.0 mm were uniformly mixed with magnetite powder. High-speed dynamic camera technology was combined with a slump-sampling method to study the mixing process of the fine coal in the fluidized bed. These results showed that limitations of the fluidized bed structure cause the mixing process to be dominated by lateral diffusion and supplemented by axial diffusion. Axial diffusion was mainly achieved through the ascension of bubbles, whereas lateral diffusion was determined by the bursting action of the gas bubbles at the surface of the bed and the undulating characteristics of the bed. The effective lateral diffusion coefficient increased exponentially with gas velocity but had no strong relationship with the bed height. As the feed point moved toward the center, fine coal began to diffuse to both sides, which shortened the time for the bed density stabilization from 20 to 5 min. The bed density of the layer was stabilized at approximately 1.75 g/cm³. The separation efficiency of the gas–solid separation fluidized bed containing binary mixtures was more obvious for 6–50 mm raw coal, with a probable error E of 0.16.

Graphical abstract

Keywords

Gas–solid separation fluidized bed; Density control; Fine coal; Diffusion behavior; Separation process

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