Reduction of slime coating: effects of sodium silicate and sodium carbonate on lean coal flotation in sodium oleate system

Abstract

High-ash fine slime has an adverse effect on coal flotation. In this study, the roles of sodium silicate (SS) and sodium carbonate (SC) in the facilitating effect on lean coal flotation (a type of coking coal) were studied when sodium oleate (NaOL) was used as a collector through flotation tests, Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS) observations, turbidity measurements, and particle interaction energy calculations. The flotation tests found that SS has a stronger capacity than SC for the improvement of flotation performance of lean coal. Moreover, SEM-EDS observations and turbidity measurements showed that SS presents a stronger weakening effect for the coating of high-ash fine slime on the surface of low-ash coal particles than SC. Furthermore, the particle interaction energy calculations verified that the increase in the energy barrier for the attachment between low-ash coal particle and high-ash fine slime caused by SS is larger than SC, providing theoretical supports for the experiments. Compared to kerosene as a collector, based on the similar ash content, the yield of clean coal increases greatly with the synergistic effect of SS and NaOL. In summary, SS is an appropriate dispersant for lean coal flotation in sodium oleate system.

HIGHLIGHTS

Effects of sodium silicate and sodium carbonate on the flotation of lean coal were studied.

Sodium silicate presents a better ash reduction effect than sodium carbonate.

Sodium silicate presents a stronger reduction effect of slime coating than sodium carbonate.

Sodium silicate greatly increases the energy barrier for the attachment between coal particle and slime.

Sodium silicate is an appropriate dispersant for the flotation of lean coal.

Graphical Abstract

Keywords:

• Lean coal flotation
• sodium silicate
• sodium carbonate
• reduction
• slime coating

Disclosure statement of interests

• The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

• The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

Zhanglei Zhu, Bohui Zhao, Jin Wang, Yiming Zhu, Qiuyue Sheng, Zhen Li, Ningning Zhang, Wei Yu

Additional information

Funding

This research was supported by the National Natural Science Foundation of China (No. 52204284) and the Natural Science Foundation of Shaanxi Province (No. 2022JQ-353 and 2024JC-YBQN-0365).