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Research on preparation and properties of porous ceramsites sintered with high-ash coal slime

Zhu Dan, Min Fanfei, Lv Wenbao

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 6

art. no. 172665

EN

In order to realize the resource and harmless utilization of high-ash coal slime in coal preparation plants, porous ceramsites were prepared by the high-temperature sintering method with coal slime as raw material. The influences of sintering temperature, sintering time and ash content on the properties of porous ceramsites were studied by experiments, and the phase composition, micro-morphology and pore structure characteristics of ceramsites were analyzed by XRD, SEM and BET. The experimental results showed that with the increase of sintering temperature and sintering time, the amount of molten liquid in ceramsite green bodies increased, the densification degree of ceramsites increased gradually, the bulk density and the apparent density increased gradually, and the water absorption and the apparent porosity decreased gradually. However, with the increase of coal slime ash content, the quantity of pores within ceramsites increased first and then decreased. When the coal slime ash content was 55%, the bulk density of porous ceramsite sample was 0.549g/cm3, the water absorption rate was 64.63%, the specific surface area was 19.40m2/g, the crushing rate and wear rate were 0.14%, with rough surface, porous structure and excellent water absorption performance, which met the optimum performance requirements of porous ceramsites. At the same time, this research also provides a new idea and method for the reuse of high-ash coal slime resource, a by-product of coal washing and dressing.

2

Utilization of coal slime: Coal and kaolinite separation by classification, forward and reverse flotation method

Shen Liang, Qiao Erle, Liu Lingyun, Xue Changguo, Liu Binghe, Min Fanfei

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 3

art. no. 147742

EN

Coal slime is not only a solid waste, but also a source of energy. With the improvement of environmental protection requirements, the comprehensive utilization of slime has become an urgent problem for coal preparation plants. In this paper, we put forward a promising way of coal slime resource utilization. X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF) and laser particle sizer was used to analyze the properties of coal slime. Obtained results showed that the slime was mainly composed of the coal, kaolinite and quartz with a particle size of -100 μm. Most kaolinite minerals can be enriched in overflow when the feed pressure is 0.2 MPa by using hydrocyclone. 21.3% clean coal with ash content of 12.3% and 33.46% kaolinite with particle size of -5 μm can be recovered by forward flotation and reverse flotation respectively. Coal water slurry with 61% concentration can be prepared from reject of forward flotation and concentrate of reverse flotation at shear rate of 100 s-1. This study has an important practical application value in clean and efficient utilization of coal.

3

Study of flocculation performance and mechanism of ultrafine montmorillonite particles with NPAM

Wang Lujun, Min Fanfei, Chen Jun, Wang Ting, Zhou Zhuang

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 3

art. no. 147790

EN

Ultrafine montmorillonite particles are the main clay minerals in industrial wastewater. In order to explore the flocculation performance and mechanism of flocculant with montmorillonite, the effects of nonionic polyacrylamide (NPAM) dosage and molecular weight on flocculation effect were studied using a flocculation sedimentation experiment. The morphology of flocs was observed by metallographic microscope and scanning electron microscope, and the microscopic adsorption mechanism was studied utilizing density functional theory (DFT). The results show that the best reagent system for the montmorillonite sample is that the molecular weight of NPAM is 14 million and the added amount is 100 g/t. The floc size increases with rising NPAM dosage, forming a unique multi-level compact space network structure through polymer bridging. The adsorption energy of acrylamide on the Na-(001) surface of montmorillonite is -108.81 kJ/mol, which is significantly higher than -50.66 kJ/mol on the None-(001) surface. Hydrogen bonding is not the main reason for the adsorption of acrylamide on the montmorillonite surface. NPAM mainly causes the flocculation and sedimentation of montmorillonite through the processes of polymer bridging and electrostatic attraction. This study can provide a theoretical basis for the design and synthesis of new flocculants.

4

Polymeric flocculants based on the interfacial characteristics of fine clay minerals : a review

Zhang Lianfeng, Min Fanfei, Wang Lujun, Shu Qingdong

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 4

art. no. 149652

EN

Fine clay minerals, found in various industrial effluents, have attracted much attention in recent times. They can form a highly stable suspension in water and increase the complexity of sedimentation for the treatment of wastewater. In the past few decades, the flocculation of fine clay minerals has been significantly improved due to numerous design advancements in the molecular weight, charge density and structure of polymeric flocculants. In this article, the interfacial characteristics and affecting factors of clay minerals are discussed, the design, synthesis and application of synthetic polymers, natural polymers and natural-based grafted polymers are reviewed, as well as the advantages and disadvantages of three types of polymers. The development direction of upgrading existing clay mineral flocculants is proposed based on the interfacial characteristics of clay minerals. Weakening the hydration of clay minerals, altering the manner of molecular interaction and precisely controlling the structure of polymer chains are the design objectives of novel polymeric flocculants.

5

Experimental study on the effect of ions on the surface hydration characteristics of fine quartz

Liu Chunfu, Min Fanfei, Liu Lingyun, Chen Jun, Ren Bao, Lv Kai, Tan Yujiao

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 4

art. no. 150280

EN

The fine quartz particle hydration and effects of metal ions on the hydration characteristics of fine quartz surface are investigated using the rheological experiment. Several important factors affecting hydration factors, such as particle sphericity, solution pH, ion species, ion concentration were investigated. The results show that viscosity and hydration factor of fine quartz suspension increase with the increase of solution pH. wherein quartz particles have more negative charges on the surface in alkaline environment and strong hydration repulsion; The introduction of metal ions enhances the hydration strength of fine quartz surface to a certain extent. In contrast, high valence and high concentration will increase the viscosity of fine quartz suspension, and the hydration factors of particle surface also increase. At the same ion concentration, the order of influence on the hydration factors of fine quartz particles is Mg2+ > Ca2+ > Na+ > K+. This finding has been attributed to the combination of metal ion hydration and its adsorption on the mineral surface. This study will provide the theoretical guiding significance for the refractory coal slime water and other mineral processing wastewater containing quartz particles.

6

Effect of ultrasonic pre-treatment on coal slime flotation

Lv Wenbao, Chen Jun, Min Fanfei, Hou Baohong, Liu Chunfu

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 1

173--183

EN

Combined with the characteristics of flotation feed originating from China’s Panyidong Coal Preparation Plant, the ash, zeta potential, X-ray fluorescence spectroscopy and contact angle test were used to study changes in the surface properties of flotation feed under ultrasonic pre-treatment, and its effect on flotation of coal slime. Results show that Preferred pre-treatment process is ultrasonic secondary treatment, ultrasonic secondary pre-treatment can remove most of the high-ash fine mud for instance kaolinite, montmorillonite and quartz in the coal slurry, reduce the surface electronegativity of coal particles, and increase the contact angle of coal particles. Thus, the concentrate ash content decreases to 13%, the recovery rate, yield of flotation concentrate and combustible matter recovery reach 92.6%, 90.9% and 97.6%, respectively.

7

Effect of dispersants on coal slime classification in a novel classification apparatus

Zhu Hongzheng, Lόpez-Valdivieso Alejandro, Zhu Jinbo, Min Fanfei

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 2

336--345

EN

The effects of the dispersants NaOH and Na2CO3 on the classification of coal slimes was studied in a novel classification apparatus. A dispersion effect was characterized through slurry pH and transmittance measurements as well as zeta potential determinations of the slimes. The pH increased and the zeta potential became more negative, while the transmittance decreased with the increase in the NaOH and Na2CO3 addition. The miscellany rates in the overflow decreased by 15.18% and 11.22% with NaOH and Na2CO3, respectively, while that in the underflow was 31.81% and 27.08%, respectively. An ash-removal efficiency from the coal slurries increased by 20.03% and 10.50% with NaOH and Na2CO3, respectively. It was found that the largest difference in classification efficiency between these dispersants in the overflow was 26.05% and underflow was 14.86%. At the high classification efficiency, the transmittance of the slurry decreased, indicating that better dispersion effect led to the higher classification efficiency of the coal slurry. NaOH showed to be a better dispersant for coal slimes classification than Na2CO3 in the novel classification apparatus.