The Experts below are selected from a list of 1650 Experts worldwide ranked by ideXlab platform
Wencheng Xia - One of the best experts on this subject based on the ideXlab platform.
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pore wetting regulation of porous active carbon by sodium oleate and its influence on particles bubble attachment a guidance for improving porous mineral Floatability
Powder Technology, 2020Co-Authors: Yuqiang Mao, Wencheng Xia, Guangyuan Xie, Yaoli PengAbstract:Abstract The pore wettability of porous minerals plays an important role in their Floatability. This paper proposed a method to reduce the pore wetting of porous active carbons using NaOL solutions with different concentrations. The in-situ pore wetting percentage of active carbon after NaOL treatments was measured by the LF-NMR and its influence on the Floatability was revealed by particles-bubble attachment tests. The action mechanism of NaOL on active carbon surface was analyzed by the contact angle, zeta potential and FTIR tests. The pore wetting percentage of active carbon were gradually decreased with the increase of concentration of NaOL solutions. NaOL could interact with hydrophilic group of active carbon surfaces through electrostatic interaction, which improved its hydrophobicity and the droplet penetrating into the pores was prevented. NaOL could reduce the pore wetting of active carbon to enhance its Floatability, which provides a potential guidance for improving porous mineral flotation.
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effects of pre wetting time on surface topography and Floatability of lignite particles
Powder Technology, 2020Co-Authors: Yuqiang Mao, Wencheng Xia, Guangyuan Xie, Yaoli PengAbstract:Abstract The laser particle size analyzer, NMR, SEM/EDS, induction time tests and surface roughness analysis were employed in the mechanism analysis of this investigation. The Floatability of lignite was decreased with the pre-wetting increasing from 0 – 5 min because the pores and fractures of lignite surface can be filled with water. However, the Floatability of lignite was increased with the pre-wetting from 5 – 480 min. NMR and SEM indicate that a long pre-wetting process (>5 min) polished and rubbed the surface of lignite reducing the amount of macropores and fractures as well as the porosity. The rough lignite surface was also polished to be smooth. As the pre-wetting time increases, the topography of lignite surface, such as porosity, macropores, fractures and roughness decreased, which results in the decrease of water filling negative effects, and hence the Floatability of lignite gradually increased with the pre-wetting time over 5 min.
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Effect of low-temperature pyrolysis on surface properties of sub-bituminous coal sample and its relationship to flotation response
Fuel, 2017Co-Authors: Niu Chenkai, Wencheng Xia, Guangyuan XieAbstract:Coal spontaneous combustion makes coal suffer a high-temperature heating process (similar to a low-temperature pyrolysis). Additionally, low rank coal is considered to be friendly utilized through two steps, i.e. low-temperature pyrolysis of low rank coal to gain gas/liquid components and then coal char forwarded to the burning or other chemical applications. Therefore, it is necessary to investigate the effect of low-temperature pyrolysis on the surface properties of low rank coal and its role in the Floatability of coal particles because coal already suffering spontaneous combustion should be upgraded before usage. In this investigation, SEM, XPS, attachment time and flotation tests were employed to reveal the changes of surface properties and Floatability of sub-bituminous coal before and after the pyrolysis. After the pyrolysis, a significant mass loss was observed and many pores/cracks were newly created as well as the content of hydrophobic functional groups on coal surface was increased whereas the content of hydrophilic oxygen-containing functional groups was reduced. The attachment time of coal-bubble was significantly decreased after the pyrolysis, which directly made an increase in the hydrophobicity and Floatability of sub-bituminous coal. The findings of this paper may be useful for a better use of sub-bituminous coal resources because sub-bituminous coal is well known as difficult to float and sub-bituminous coal fines are usually wasted in coal preparation plants. This paper proposes that coal char from sub-bituminous coal may be forwarded to a further upgrading process (i.e. flotation) because the Floatability of sub-bituminous coal is significantly improved by the pyrolysis.
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Enhancement in Floatability of sub-bituminous coal by low-temperature pyrolysis and its potential application in coal cleaning
Journal of Cleaner Production, 2017Co-Authors: Wencheng Xia, Chenkai Niu, Chuancheng RenAbstract:Sub-bituminous coal is one type of low rank coal, which is difficult to upgrade using flotation cleaning technology because of its high hydrophilic properties. Low-temperature pyrolysis is widely used to convert low rank coal to gas/liquid components and the coal char is burned for power generation. It is friendlier to the environment if the coal char is forwarded to the cleaning process prior to the burning/combustion. This investigation aimed to assess the possibility of upgrading the coal char obtained from the low-temperature pyrolysis of sub-bituminous coal. The scanning electron microscopy, X-ray photoelectron spectroscopy, attachment time, and flotation tests were used to reveal the changes of surface properties and Floatability of sub-bituminous coal during low-temperature pyrolysis with different pyrolysis times, i.e. 30, 60, 90, and 120 min, respectively. The results indicated that many pores and cracks were created on the coal char compared to raw coal surface. The content of hydrophobic functional groups on coal surface was increased whereas the content of hydrophilic oxygen-containing functional groups on the coal surface was reduced after the pyrolysis. The attachment time of coal particle-bubble was significantly decreased while the flotation recovery of coal was increased after the pyrolysis. Throughout this paper, the pyrolysis time of 30 min may be suitable for the enhancement of coal Floatability by considering the gas/liquid production as well as economy and time saving. It is also inferred that the Floatability of coal char should be governed by both its surface morphology and its surface composition of functional groups.
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Role of particle shape in the Floatability of mineral particle: An overview of recent advances
Powder Technology, 2017Co-Authors: Wencheng XiaAbstract:Particle shape is an important factor that affects the Floatability of mineral particle. However, it is difficult to investigate the dependence of particle shape on mineral flotation because the limited accuracy of shape characterization though various methods of shape characterization have been proposed in the literature. This review not only overviews the methods to characterize particle shape, but also highlights recent investigations into the role of particle shape in the Floatability of various particles, such as gold, magnetite, chalcopyrite, pyrite, molybdenite, alumina, galena, sphalerite, muscovite, talc, quartz, glass beads, borosilicate glass, calcite, barite, plastic, ink and coal. Finally, the mechanism of particle shape affecting the Floatability of mineral particle will be also discussed.
Guangyuan Xie - One of the best experts on this subject based on the ideXlab platform.
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pore wetting regulation of porous active carbon by sodium oleate and its influence on particles bubble attachment a guidance for improving porous mineral Floatability
Powder Technology, 2020Co-Authors: Yuqiang Mao, Wencheng Xia, Guangyuan Xie, Yaoli PengAbstract:Abstract The pore wettability of porous minerals plays an important role in their Floatability. This paper proposed a method to reduce the pore wetting of porous active carbons using NaOL solutions with different concentrations. The in-situ pore wetting percentage of active carbon after NaOL treatments was measured by the LF-NMR and its influence on the Floatability was revealed by particles-bubble attachment tests. The action mechanism of NaOL on active carbon surface was analyzed by the contact angle, zeta potential and FTIR tests. The pore wetting percentage of active carbon were gradually decreased with the increase of concentration of NaOL solutions. NaOL could interact with hydrophilic group of active carbon surfaces through electrostatic interaction, which improved its hydrophobicity and the droplet penetrating into the pores was prevented. NaOL could reduce the pore wetting of active carbon to enhance its Floatability, which provides a potential guidance for improving porous mineral flotation.
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effects of pre wetting time on surface topography and Floatability of lignite particles
Powder Technology, 2020Co-Authors: Yuqiang Mao, Wencheng Xia, Guangyuan Xie, Yaoli PengAbstract:Abstract The laser particle size analyzer, NMR, SEM/EDS, induction time tests and surface roughness analysis were employed in the mechanism analysis of this investigation. The Floatability of lignite was decreased with the pre-wetting increasing from 0 – 5 min because the pores and fractures of lignite surface can be filled with water. However, the Floatability of lignite was increased with the pre-wetting from 5 – 480 min. NMR and SEM indicate that a long pre-wetting process (>5 min) polished and rubbed the surface of lignite reducing the amount of macropores and fractures as well as the porosity. The rough lignite surface was also polished to be smooth. As the pre-wetting time increases, the topography of lignite surface, such as porosity, macropores, fractures and roughness decreased, which results in the decrease of water filling negative effects, and hence the Floatability of lignite gradually increased with the pre-wetting time over 5 min.
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study on the effects of pre conditioning time on the Floatability of molybdenite from the perspective of cavitation threshold
Minerals Engineering, 2019Co-Authors: Vu N T Truong, Yuran Chen, Yaoli Peng, Guangyuan XieAbstract:Abstract In flotation processes, mineral particles are separated based on different surface physicochemical properties. The surface of molybdenite consists of both hydrophobic and hydrophilic faces, meaning this particular structure can lead to a reduction in Floatability when molybdenite is treated using long-time stirring and ultrasound. In this study, an acoustic method called high-intensity focused ultrasound was applied to detect the nuclei in a molybdenite suspension before and after long-duration pre-conditioning. The cavitation threshold (liquid pressure at 50% cavitation probability) was then calculated based on numerous cavitation results, which were applied to characterize the wettability of molybdenite particles in water. Additionally, particle size measurements and X-ray photoelectron spectroscopy analysis were employed to highlight the differences in particle properties after long-duration pre-conditioning. However, these tests cannot fully elucidate the changes in Floatability of molybdenite in water. Nano-bubbles on particle surfaces were determined to be the main cause for the high Floatability of molybdenite. This study will present insights into the vital role of pretreatment time on the Floatability of molybdenite. We also propose a method for determining the wettability of particles in water.
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Effect of low-temperature pyrolysis on surface properties of sub-bituminous coal sample and its relationship to flotation response
Fuel, 2017Co-Authors: Niu Chenkai, Wencheng Xia, Guangyuan XieAbstract:Coal spontaneous combustion makes coal suffer a high-temperature heating process (similar to a low-temperature pyrolysis). Additionally, low rank coal is considered to be friendly utilized through two steps, i.e. low-temperature pyrolysis of low rank coal to gain gas/liquid components and then coal char forwarded to the burning or other chemical applications. Therefore, it is necessary to investigate the effect of low-temperature pyrolysis on the surface properties of low rank coal and its role in the Floatability of coal particles because coal already suffering spontaneous combustion should be upgraded before usage. In this investigation, SEM, XPS, attachment time and flotation tests were employed to reveal the changes of surface properties and Floatability of sub-bituminous coal before and after the pyrolysis. After the pyrolysis, a significant mass loss was observed and many pores/cracks were newly created as well as the content of hydrophobic functional groups on coal surface was increased whereas the content of hydrophilic oxygen-containing functional groups was reduced. The attachment time of coal-bubble was significantly decreased after the pyrolysis, which directly made an increase in the hydrophobicity and Floatability of sub-bituminous coal. The findings of this paper may be useful for a better use of sub-bituminous coal resources because sub-bituminous coal is well known as difficult to float and sub-bituminous coal fines are usually wasted in coal preparation plants. This paper proposes that coal char from sub-bituminous coal may be forwarded to a further upgrading process (i.e. flotation) because the Floatability of sub-bituminous coal is significantly improved by the pyrolysis.
Xiahui Gui - One of the best experts on this subject based on the ideXlab platform.
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a new experimental approach to evaluate coal particles Floatability bubble particle attachment and detachment kinetics
ACS omega, 2020Co-Authors: Lijuan Sun, Yijun Cao, Yaowen Xing, Haichang Yang, Xiahui GuiAbstract:Coal Floatability evaluation is of vital importance in the prediction of flotation results and the design of a flotation flowsheet. In this work, a new experimental approach based on bubble–particl...
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effect of heating oxidation on the surface interface properties and Floatability of anthracite coal
Processes, 2019Co-Authors: Guoqiang Rong, Xiahui Gui, Dongyue Wang, Yaowen XingAbstract:Oxidation processes of coal surfaces are both fundamental and interesting from academic and engineering points of view. In this work, we comprehensively analyzed the mechanism of heating oxidation at 200 °C on the surface/interface characters and the Floatability of anthracite coal. The variations of surface/interface characters were studied using SEM (scanning electron microscopy), FTIR (Fourier transform infrared spectroscopy), and XPS (X-ray photoelectron spectroscopy). The Floatability was further identified using Induction Time and Bubble-Particle Wrap Angle. It was found that, after heating oxidation at 200 °C, both surface ravines and oxygen-containing groups were increased. The degradation of hydroxyl on anthracite could be neglected during the heating, while the oxidation of hydrocarbon chains dominated the balance of hydrophobicity and hydrophilicity on coal surface. The induction time significantly increased from 200 ms to 1200 ms and 2000 ms after 10 h and 20 h of heating oxidation at 200 °C, respectively. Additionally, raw coal exhibited the fastest kinetics of bubble-particle attachment and the largest wrap angle, directly proving that the Floatability decreased after oxidation.
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improving the Floatability of coal with varying surface roughness through hypobaric treatment
Powder Technology, 2019Co-Authors: Yaowen Xing, Yijun Cao, Fangyu Guo, Youfei Zhang, Min Liu, Haisheng Han, Zhiyong Gao, Xiahui GuiAbstract:Abstract Surface roughness has a great impact on coal Floatability, and usually the effect is found to be negative. In this paper, hypobaric treatment was introduced to improve the Floatability of coal with varying surface roughness. The Floatability was characterized by induction time, and the micro-bubble nucleation theory was proposed to explain the enhancement mechanism of hypobaric treatment. The results show that the induction time was increased with increasing surface roughness. However, hypobaric treatment was proven to be an effective method in mitigating the adverse effects of surface roughness on Floatability. Under natural conditions, neither Wenzel nor Cassie model could be used to describe the wetting regime of coal surface. Instead, a mixed wetting state, where water partially wets the asperities on coal surface and partially sits on entrapped air pockets, was more appropriate. It was difficult to drain the entrapped water at the upper part of the grooves; hence, bubble-coal attachment was prevented, leading to the increased induction time at high surface roughness. After hypobaric treatment, the diffused gas molecules in water preferred to nucleate at the sites of air pockets, leading to the formation of micro-bubbles. These micro-bubbles would act as the bridge between macroscopic bubbles and the coal surface, significantly decreasing induction time and improving the coal contact angle and Floatability.
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role of different types of clay in the Floatability of coal induction time and bubble particle attachment kinetics analysis
Powder Technology, 2019Co-Authors: Yaowen Xing, Yijun Cao, Fangyu Guo, Jiaqian Luo, Youfei Zhang, Xiahui GuiAbstract:Abstract The presence of clay minerals presents a great challenge to fine coal and mineral flotation due to the well-known phenomena of mechanical coating and water entrainment. In this paper, we study the effect of two different types of clay, kaolinite and montmorillonite, on the Floatability of coal in de-ionized water (without flotation reagents) based on induction time and bubble-particle attachment kinetics. The bubble-particle attachment angle (BPAA) as a function of time was used as the kinetics raw data. We demonstrated how the presence of montmorillonite was detrimental to the Floatability of coal in de-ionized water. This was not the case with kaolinite. The induction time and BPAA kinetics of coal particles only changed slightly after conditioning together with kaolinite. In contrast, the induction time increased considerably from 8.73 ms to 83.25 ms when montmorillonite was added. In addition, both the maximum BPAA and BPAA kinetics constant decreased, and hydrophilic montmorillonite coating occurred during the conditioning stage. These hydrophilic sites on the coal surface prevent the thinning-rupture of the water film between bubble and coal particles and thus decrease the Floatability and recovery.
Chuancheng Ren - One of the best experts on this subject based on the ideXlab platform.
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Enhancement in Floatability of sub-bituminous coal by low-temperature pyrolysis and its potential application in coal cleaning
Journal of Cleaner Production, 2017Co-Authors: Wencheng Xia, Chenkai Niu, Chuancheng RenAbstract:Sub-bituminous coal is one type of low rank coal, which is difficult to upgrade using flotation cleaning technology because of its high hydrophilic properties. Low-temperature pyrolysis is widely used to convert low rank coal to gas/liquid components and the coal char is burned for power generation. It is friendlier to the environment if the coal char is forwarded to the cleaning process prior to the burning/combustion. This investigation aimed to assess the possibility of upgrading the coal char obtained from the low-temperature pyrolysis of sub-bituminous coal. The scanning electron microscopy, X-ray photoelectron spectroscopy, attachment time, and flotation tests were used to reveal the changes of surface properties and Floatability of sub-bituminous coal during low-temperature pyrolysis with different pyrolysis times, i.e. 30, 60, 90, and 120 min, respectively. The results indicated that many pores and cracks were created on the coal char compared to raw coal surface. The content of hydrophobic functional groups on coal surface was increased whereas the content of hydrophilic oxygen-containing functional groups on the coal surface was reduced after the pyrolysis. The attachment time of coal particle-bubble was significantly decreased while the flotation recovery of coal was increased after the pyrolysis. Throughout this paper, the pyrolysis time of 30 min may be suitable for the enhancement of coal Floatability by considering the gas/liquid production as well as economy and time saving. It is also inferred that the Floatability of coal char should be governed by both its surface morphology and its surface composition of functional groups.
Yaowen Xing - One of the best experts on this subject based on the ideXlab platform.
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a new experimental approach to evaluate coal particles Floatability bubble particle attachment and detachment kinetics
ACS omega, 2020Co-Authors: Lijuan Sun, Yijun Cao, Yaowen Xing, Haichang Yang, Xiahui GuiAbstract:Coal Floatability evaluation is of vital importance in the prediction of flotation results and the design of a flotation flowsheet. In this work, a new experimental approach based on bubble–particl...
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effect of heating oxidation on the surface interface properties and Floatability of anthracite coal
Processes, 2019Co-Authors: Guoqiang Rong, Xiahui Gui, Dongyue Wang, Yaowen XingAbstract:Oxidation processes of coal surfaces are both fundamental and interesting from academic and engineering points of view. In this work, we comprehensively analyzed the mechanism of heating oxidation at 200 °C on the surface/interface characters and the Floatability of anthracite coal. The variations of surface/interface characters were studied using SEM (scanning electron microscopy), FTIR (Fourier transform infrared spectroscopy), and XPS (X-ray photoelectron spectroscopy). The Floatability was further identified using Induction Time and Bubble-Particle Wrap Angle. It was found that, after heating oxidation at 200 °C, both surface ravines and oxygen-containing groups were increased. The degradation of hydroxyl on anthracite could be neglected during the heating, while the oxidation of hydrocarbon chains dominated the balance of hydrophobicity and hydrophilicity on coal surface. The induction time significantly increased from 200 ms to 1200 ms and 2000 ms after 10 h and 20 h of heating oxidation at 200 °C, respectively. Additionally, raw coal exhibited the fastest kinetics of bubble-particle attachment and the largest wrap angle, directly proving that the Floatability decreased after oxidation.
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improving the Floatability of coal with varying surface roughness through hypobaric treatment
Powder Technology, 2019Co-Authors: Yaowen Xing, Yijun Cao, Fangyu Guo, Youfei Zhang, Min Liu, Haisheng Han, Zhiyong Gao, Xiahui GuiAbstract:Abstract Surface roughness has a great impact on coal Floatability, and usually the effect is found to be negative. In this paper, hypobaric treatment was introduced to improve the Floatability of coal with varying surface roughness. The Floatability was characterized by induction time, and the micro-bubble nucleation theory was proposed to explain the enhancement mechanism of hypobaric treatment. The results show that the induction time was increased with increasing surface roughness. However, hypobaric treatment was proven to be an effective method in mitigating the adverse effects of surface roughness on Floatability. Under natural conditions, neither Wenzel nor Cassie model could be used to describe the wetting regime of coal surface. Instead, a mixed wetting state, where water partially wets the asperities on coal surface and partially sits on entrapped air pockets, was more appropriate. It was difficult to drain the entrapped water at the upper part of the grooves; hence, bubble-coal attachment was prevented, leading to the increased induction time at high surface roughness. After hypobaric treatment, the diffused gas molecules in water preferred to nucleate at the sites of air pockets, leading to the formation of micro-bubbles. These micro-bubbles would act as the bridge between macroscopic bubbles and the coal surface, significantly decreasing induction time and improving the coal contact angle and Floatability.
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role of different types of clay in the Floatability of coal induction time and bubble particle attachment kinetics analysis
Powder Technology, 2019Co-Authors: Yaowen Xing, Yijun Cao, Fangyu Guo, Jiaqian Luo, Youfei Zhang, Xiahui GuiAbstract:Abstract The presence of clay minerals presents a great challenge to fine coal and mineral flotation due to the well-known phenomena of mechanical coating and water entrainment. In this paper, we study the effect of two different types of clay, kaolinite and montmorillonite, on the Floatability of coal in de-ionized water (without flotation reagents) based on induction time and bubble-particle attachment kinetics. The bubble-particle attachment angle (BPAA) as a function of time was used as the kinetics raw data. We demonstrated how the presence of montmorillonite was detrimental to the Floatability of coal in de-ionized water. This was not the case with kaolinite. The induction time and BPAA kinetics of coal particles only changed slightly after conditioning together with kaolinite. In contrast, the induction time increased considerably from 8.73 ms to 83.25 ms when montmorillonite was added. In addition, both the maximum BPAA and BPAA kinetics constant decreased, and hydrophilic montmorillonite coating occurred during the conditioning stage. These hydrophilic sites on the coal surface prevent the thinning-rupture of the water film between bubble and coal particles and thus decrease the Floatability and recovery.