Efficient separation of high-ash fine coal by the collaboration of nanobubbles and polyaluminum chloride

Li, Chenwei; Xu, Ming; Zhang, Haijun

doi:10.1016/j.fuel.2019.116325

Cited by 26 publications

(23 citation statements)

References 43 publications

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“…The PW discharged from the pressure tank immediately is milky white, as shown in Figure a. After a few minutes, the milky white disappeared and the PW looked like OW . An image of this change is shown in Figure b.…”

Section: Methodsmentioning

confidence: 95%

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Influence of Air Solubility on the Flotation Performance of Low-Rank Coal

et al. 2022

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Low-rank coal (LRC) contains large amounts of harmful impurities that must be processed before utilization. Flotation is an effective means for separating fine particles, which can be influenced by air solubility in water. In this work, deaerated water (DW), ordinary water (OW), and pressurized water (PW) were prepared to research the underlying mechanism of the effect of air solubility on the flotation performance of LRC. The results show that PW dissolves the greatest amount of air in the three kinds of water (DW, OW, and PW). The flotation performance of LRC in different water types is directly proportional to air solubility in aqueous solutions. In addition, the induction time of LRC in PW (600 ms) is significantly shorter than those in OW (1200 ms) and DW (4000 ms). Atomic force microscopy (AFM) studies reveal that typical interfacial nanobubbles (NBs) only form on a highly oriented pyrolytic graphite (HOPG) surface in PW due to the supersaturated air in water. Furthermore, the interaction between LRC particles and HOPG in PW is significantly stronger than those in both OW and DW, which is attributed to the capillary force of rgw nanobubble bridge formed between particles. The hydrophobic interaction enhanced by NBs is critically important for the attachment of LRC particles to macrobubbles in flotation. Overall, air solubility in water has a great effect on LRC flotation performance, and PW flotation technology can be extended to LRC purification.

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Section: Methodsmentioning

confidence: 95%

“…After a few minutes, the milky white disappeared and the PW looked like OW. 35 An image of this change is shown in Figure 2b. However, when a laser (2801G, Deli Group Co., Ltd., China) is used to irradiate the PW, a red beam can be seen (Figure 2c), which is not seen in OW (Figure 2d).…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Influence of Air Solubility on the Flotation Performance of Low-Rank Coal

et al. 2022

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“…After settling for a given time length, the top 250 mL suspension was taken out via a valve in the wall of the cylinder and dried at 80 °C to measure the mass of remaining solids. The results of the settling tests were recorded as settling efficiency ( E s ), 31 which is defined as where m and m 0 represent the mass of solids in the top 250 mL suspension before and after settling, respectively.…”

Section: Methodsmentioning

confidence: 99%

Effect of Nanobubbles on the Slime Coating of Kaolinite in Coal Flotation

Zhang

Wang

et al. 2020

ACS Omega

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Understanding the coating behavior of fine gangue slimes in the presence of nanobubbles (NBs) is important for the application of NB technology in flotation. In this study, slime coating of kaolinite in the flotation of a low-ash coal using deionized (DI) water and NB water was investigated. Kaolinite was found to depress coal flotation by the formation of coating on coal surfaces, but its deleterious effect was less pronounced in the NB water with mitigated slime coating. Setting tests, Brunauer–Emmett–Teller surface area measurements, and dynamic light scattering were conducted to understand the underpinning mechanism. In comparison with DI water, the degree of kaolinite aggregation was enhanced in the NB water. The intensified self-aggregation of kaolinite platelets which appears to be induced by the presence of NBs reduces the solid–liquid interfacial area as well as the number of free kaolinite particles in the suspension, mitigating the coating of kaolinite on coal surfaces in NB water flotation.

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“…They can rapidly attach to the hydrophobic mineral surfaces and thereby enhance the flotation efficiency and recovery by promoting the aggregation of fine and ultrafine mineral particles through capillary effect and by acting as nuclei for conventional flotation-sized bubbles to adhere. − Li et al revealed that the use of the water containing NBs increased the combustible recovery because of the increased apparent size of fine coal particles in the presence of NBs, while simultaneously increasing the entrainment recovery of clay particles to the concentrate. In the same study, PAC was then introduced to NB water flotation, and it was found that while the direct addition of PAC to NB water did alleviate the high kaolinite entrainment, this method also reduced the combustible recovery because PAC had a detrimental effect on the surface hydrophobicity of coal particles . Clearly, these reported strategies were either not practical or had the common shortcoming of not being able to achieve high recovery of fine coal and low gangue entrainment at the same time.…”

Section: Introductionmentioning

confidence: 99%

Effective Separation of High-Ash Fine Coal Using Water Containing Positively Charged Nanobubbles and Polyaluminum Chloride

Zhang

Yao

et al. 2022

ACS Omega

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The coal industry is facing the challenge of treating high-ash fine coal. In this study, we proposed an effective method to handle high-ash fine coal using water containing positively charged nanobubbles (PCNBs) and polyaluminum chloride (PAC). For comparison, normal nanobubble (NB) water was tested in parallel. Flotation results of a modeled high-ash fine coal showed that compared to the use of NBs alone, an enhanced combustible recovery with a simultaneous reduction in ash recovery was obtained when using water containing PCNBs and PAC. Particle size distribution together with particle video microscopy (PVM) and the degree of entrainment analysis were conducted to understand the underpinning mechanism. It was found that the presence of PCNBs intensified the aggregation of fine coal particles, which accounted for the boosted combustible recovery. It was interesting that PAC could disrupt coal flocs induced by NBs, leading to the release of trapped kaolinite particles with alleviated clay recovery by entrapment.

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Efficient separation of high-ash fine coal by the collaboration of nanobubbles and polyaluminum chloride

Cited by 26 publications

References 43 publications

Influence of Air Solubility on the Flotation Performance of Low-Rank Coal

Influence of Air Solubility on the Flotation Performance of Low-Rank Coal

Effect of Nanobubbles on the Slime Coating of Kaolinite in Coal Flotation

Effective Separation of High-Ash Fine Coal Using Water Containing Positively Charged Nanobubbles and Polyaluminum Chloride

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