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11 pages, 2810 KiB

Open AccessArticle

Oscillatory Rheology of Three-Phase Coal Froths: Effects of Ionic Strength

by Na Zhang, Jue Kou, Chunbao Sun and Yangge Zhu

Processes 2023, 11(9), 2569; https://doi.org/10.3390/pr11092569 - 27 Aug 2023

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The rheologic properties of a three-phase coal froth are critical to understanding the interfacial properties that are associated with its stability. Due to the fragile nature of froth, oscillatory rheology was used to make sure that the froths were not damaged during measurement. [...] Read more.

The rheologic properties of a three-phase coal froth are critical to understanding the interfacial properties that are associated with its stability. Due to the fragile nature of froth, oscillatory rheology was used to make sure that the froths were not damaged during measurement. To reveal the relationship between a coal froth’s rheology and its stability, oscillatory rheology was used in this study. The viscoelastic behaviors of coal froths were analyzed, which illustrated that the storage modulus (G′) of a coal froth is larger than its loss modulus (G″), showing that coal froth is solid-like. The complex viscosity of the coal froths decreased with an increase in angular frequency, meaning that coal froth is shear-thinning. The dependence of froth rheology on ionic strength was investigated, which showed that an increase in ionic strength led to an enhancement of the storage modulus G′, as well as a decrease in tanδ (G″/G′). The coal froths tended to be more rigid and viscous with an increase in ionic strength. The mechanism of the effect of ionic strength on froth rheology was explored using electrical double layers, cryo-SEM, and particle fractions. As the ionic strength increased, the thickness of the electrical double layer decreased, which strengthened the interaction between the particles in the froth; in addition, the solid fraction in the froth increased with an increase in the ionic strength, so the value of G′ and the froth’s stability both increased. Full article

(This article belongs to the Special Issue Process Analysis and Carbon Emission of Mineral Separation Processes)

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13 pages, 3558 KiB

Open AccessArticle

Flotation Characteristics of Amphibole-Type Oxidized Iron Ore via Reverse Anionic Flotation

by Mingzhu Huangfu, Yiming Hu, Yongcheng Zhou, Mingyang Li, Jiushuai Deng, Shan Li and Guixiong Peng

Processes 2023, 11(8), 2388; https://doi.org/10.3390/pr11082388 - 08 Aug 2023

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Abstract

To explore the flotation feasibility and flotation law of iron minerals from amphibole-type iron oxide ore with full-size minerals, a systematic study on the flotation behaviors of single minerals hematite, quartz, and amphibole was carried out with the anionic reverse flotation system. The [...] Read more.

To explore the flotation feasibility and flotation law of iron minerals from amphibole-type iron oxide ore with full-size minerals, a systematic study on the flotation behaviors of single minerals hematite, quartz, and amphibole was carried out with the anionic reverse flotation system. The effects of collectors, depressants, activators, and pH on the floatabilities of three single minerals was investigated. The flotation separations of binary mixed minerals and ternary mixed ores were carried out, respectively. The study results show that CaCl₂ is adsorbed on the surfaces of quartz and amphibole, which can activate them. The hydroxyl groups of the starch molecular chain were adsorbed on the surfaces of the hematite and amphibole in the form of hydrogen bonds, but were hardly adsorbed on surface of the quartz. Therefore, both hematite and amphibole were depressed, resulting in a poor separation effect of the three single minerals in the anionic flotation system. Full article

(This article belongs to the Special Issue Process Analysis and Carbon Emission of Mineral Separation Processes)

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15 pages, 8958 KiB

Open AccessArticle

Study on Mechanism of MSWI Fly Ash Solidified by Multiple Solid Waste-Based Cementitious Material Using the Rietveld Method

by Xiaoli Wang, Pingfeng Fu, Wei Deng, JinJin Shi and Miao Xu

Processes 2023, 11(8), 2311; https://doi.org/10.3390/pr11082311 - 01 Aug 2023

Cited by 2 | Viewed by 819

Abstract

A novel multiple solid waste-based cementitious material (MSWCM) was developed to immobilize municipal solid waste incineration (MSWI) fly ash. The compressive strength of MSWCM with different ratios of MSWI fly ash reached the standard requirements after curing for 28 days. X-ray powder diffraction [...] Read more.

A novel multiple solid waste-based cementitious material (MSWCM) was developed to immobilize municipal solid waste incineration (MSWI) fly ash. The compressive strength of MSWCM with different ratios of MSWI fly ash reached the standard requirements after curing for 28 days. X-ray powder diffraction (XRD) in combination with the Rietveld method was employed to investigate the content and phase transformation of hydration products. The main hydration products of pure MSWCM paste were C-S-H, hydroxyapatite, ettringite and C-A-S-H. With increases in curing time, the content of ettringite and C-A-S-H increased significantly. The main hydration products of MSWCM paste with MSWI fly ash were C-S-H and Friedel’s salt. The contents increased markedly with increased curing time from 21.8% to 28.0% and from 8.53% to 16.7%, respectively. Additionally, a small amount of PbHPO₄ (0.51–0.96%) and lead phosphate Pb₃(PO₄)₂ (0.14–0.51%) were detected, indicating that phosphate had an effective curing effect on lead ions. The results showed that most of the hydration reactions had started at the initial stage of curing and reacted quickly to form a large number of hydration products. The quantitative analyses of hydration products provide essential information for understanding the immobilization mechanism of MSWI fly ash in MSWCM paste. Full article

(This article belongs to the Special Issue Process Analysis and Carbon Emission of Mineral Separation Processes)

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11 pages, 2829 KiB

Open AccessArticle

Changes in Surface Hydrophobicity of Coal Particles and the Formation of Coarse Particle–Bubble Clusters in the Process of High-Intensity Conditioning

by Xiaofu Jia, Yuexian Yu, Jiahui Liu, Chen Min, Fan Liu, Ningning Zhang, Songjiang Chen and Zhanglei Zhu

Processes 2023, 11(6), 1723; https://doi.org/10.3390/pr11061723 - 05 Jun 2023

Cited by 2 | Viewed by 984

Abstract

The mechanism of high-intensity conditioning (HIC) has not been thoroughly revealed, and therefore this work investigates the effect of HIC on the surface hydrophobicity of coal with different particle sizes and the possible formation of particle–bubble clusters. The results show that different HIC [...] Read more.

The mechanism of high-intensity conditioning (HIC) has not been thoroughly revealed, and therefore this work investigates the effect of HIC on the surface hydrophobicity of coal with different particle sizes and the possible formation of particle–bubble clusters. The results show that different HIC conditions are required for coarse and fine particles. Coarse particles (+75 μm) require a higher turbulence intensity to increase collector dispersion, thereby increasing the adsorption of the collector. Fine particles (−75 μm) require a lower turbulence intensity to reduce the desorption of the collector. In this study, the optimum HIC conditions for coarse and fine particles are “2200 rpm + 1 min” and “1300 rpm + 1 min”, respectively. Interestingly, it seems that the adsorption capacity between fine particles and the collector is weaker than that for coarse particles. A non-enclosed HIC system produces up to 1.78 × 10⁴/g bubbles in coarse particle–bubble clusters, and the mean bubble diameter is approximately 87 μm. The cluster achieves pre-mineralization and increases the apparent particle size, which is expected to improve flotation. Full article

(This article belongs to the Special Issue Process Analysis and Carbon Emission of Mineral Separation Processes)

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17 pages, 3090 KiB

Open AccessArticle

The Combustion of Forest Humus Blended with Low-Rank Coal: Effects of Oxygen Ratio and Blending Ratio

by Guoli Zhou, Tong Zhang, Chenfei Lou, Kunpeng Wang, Qinghang Yun, Peng Li, Xiaoyang Qu and Guosheng Li

Processes 2023, 11(6), 1615; https://doi.org/10.3390/pr11061615 - 25 May 2023

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Abstract

In this study, the combustion characteristics of pine needles, pine needle humus, and the co-combustion of these two types of biomass with coal were compared. In addition, the optimization of the combustion performance of coal/humus was assisted through the following studies: (i) the [...] Read more.

In this study, the combustion characteristics of pine needles, pine needle humus, and the co-combustion of these two types of biomass with coal were compared. In addition, the optimization of the combustion performance of coal/humus was assisted through the following studies: (i) the combustion performance of coal/pine needle humus was studied under four different oxygen concentrations (N₂, 10%O₂/90%N₂, 20%O₂/80%N₂, and 40%O₂/60%N₂); (ii) the synergistic effect between the humus and coal during combustion was also investigated by adjusting the blending ratio and oxygen content; (iii) the mechanisms of the optimized combustion processes were expounded by kinetics and thermodynamics discussion. The results demonstrated that the combustion characteristics of the coal/humus blends were found to be higher than those of the coal/pine needle blends. The coupling interactions of the oxygen content and blending ratio contributed to the significant synergistic effect between the two fuels, and the synergistic effect showed a nonlinear variation with an increased oxygen concentration. The synergistic effect in a rich oxygen environment (O₂40%/N₂60%) is 5.1 times greater than that in the synthetic air (O₂20%/N₂80%) and 13.8 times greater than that in the oxygen-poor environment (O₂10%/N₂90%). Hence, the blending ratio could be adjusted to maintain the intensity of the synergistic effect in an oxygen-rich atmosphere. Full article

(This article belongs to the Special Issue Process Analysis and Carbon Emission of Mineral Separation Processes)

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16 pages, 1427 KiB

Open AccessArticle

Construction of a Green-Comprehensive Evaluation System for Flotation Collectors

by Hongxiang Xu, Jiahua Cui, Yijun Cao, Lin Ma, Guixia Fan, Gen Huang, Kejia Ning, Jingzheng Wang, Yuntao Kang, Xin Sun, Jiushuai Deng and Shan Li

Processes 2023, 11(5), 1563; https://doi.org/10.3390/pr11051563 - 19 May 2023

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Abstract

The evaluation of flotation reagents performs an important role in the selection and green application of reagents. The green indexes and effect indexes of flotation collectors were selected by data literature method, system analysis method, mathematical model method, and qualitative and quantitative analysis [...] Read more.

The evaluation of flotation reagents performs an important role in the selection and green application of reagents. The green indexes and effect indexes of flotation collectors were selected by data literature method, system analysis method, mathematical model method, and qualitative and quantitative analysis method, and the green evaluation system of flotation collectors, flotation effect evaluation system, and comprehensive evaluation system of flotation collectors were established. The normalization method and expert evaluation methods were adopted to obtain the grade classification of quantitative and qualitative indicators, respectively. The analytic hierarchy process (AHP) was used to determine the weight of secondary indicators and tertiary indicators of the evaluation system and the weight of indicators at a lower level. Applying the fuzzy comprehensive evaluation (FCE), the trapezoidal function is selected to determine the index affiliation, the index system score is calculated according to the weighted average principle, and finally, the established evaluation system is applied in an example. The example application shows that the comprehensive evaluation system of flotation collectors can make a comprehensive evaluation of collectors from the aspects of the greenness of reagent, flotation effect, and cost, and it has a strong target and practicality for collectors evaluation. The establishment of the system has a guiding significance for the selection and use of flotation collectors. Full article

(This article belongs to the Special Issue Process Analysis and Carbon Emission of Mineral Separation Processes)

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19 pages, 4427 KiB

Open AccessArticle

Lightweight Target Detection for Coal and Gangue Based on Improved Yolov5s

by Zhenguan Cao, Liao Fang, Zhuoqin Li and Jinbiao Li

Processes 2023, 11(4), 1268; https://doi.org/10.3390/pr11041268 - 19 Apr 2023

Cited by 4 | Viewed by 1052

Abstract

The detection of coal and gangue is an essential part of intelligent sorting. A lightweight coal and gangue detection algorithm based on You Only Look Once version 5s (Yolov5s) is proposed for the current coal and gangue target detection algorithm with the low [...] Read more.

The detection of coal and gangue is an essential part of intelligent sorting. A lightweight coal and gangue detection algorithm based on You Only Look Once version 5s (Yolov5s) is proposed for the current coal and gangue target detection algorithm with the low accuracy of small target detection, high model complexity, and sizeable computational memory consumption. Firstly, we build a new convolutional block based on the Funnel Rectified Linear Unit (FReLU) activation function and apply it to the original Yolov5s network so that the model adaptively captures local contextual information of the image. Secondly, the neck of the original network is redesigned to improve the detection accuracy of small samples by adding a small target detection head to achieve multi-scale feature fusion. Next, some of the standard convolution modules in the original network are replaced with Depthwise Convolution (DWC) and Ghost Shuffle Convolution (GSC) modules to build a lightweight feature extraction network while ensuring the model detection accuracy. Finally, an efficient channel attention (ECA) module is embedded in the backbone of the lightweight network to facilitate accurate localization of the prediction region by improving the information interaction of the model with the channel features. In addition, the importance of each component is fully demonstrated by ablation experiments and visualization analysis comparison experiments. The experimental results show that the mean average precision (mAP) and the model size of our proposed model reach 0.985 and 4.9 M, respectively. The mAP is improved by 0.6%, and the number of parameters is reduced by 72.76% compared with the original Yolov5s network. The improved algorithm has higher localization and recognition accuracy while significantly reducing the number of floating-point calculations and of parameters, reducing the dependence on hardware, and providing a specific reference basis for deploying automated underground gangue sorting. Full article

(This article belongs to the Special Issue Process Analysis and Carbon Emission of Mineral Separation Processes)

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11 pages, 2800 KiB

Open AccessFeature PaperArticle

A Measurement Method for the Pore Structure of Coal Slime Filter Cake

by Libo Liu, Qiming Zhuo, Hongxiang Xu and Donghui Wang

Processes 2023, 11(1), 102; https://doi.org/10.3390/pr11010102 - 29 Dec 2022

Cited by 3 | Viewed by 916

Abstract

The accurate determination of the coal slime filter cake pore structure has always been a problem in the field of solid–liquid separation. An innovative measurement method for the pore structure of filter cake after filtration dehydration of coal slime water, including the preparation [...] Read more.

The accurate determination of the coal slime filter cake pore structure has always been a problem in the field of solid–liquid separation. An innovative measurement method for the pore structure of filter cake after filtration dehydration of coal slime water, including the preparation of coal slime filter cake, the solidification of the filter cake, and the preparation and measurement of test filter cake, was established in this paper. Epoxy resin and curing agent can ensure the strength of the filter cake, and red colorant can realize the accurate separation of coal particles and pores. The most suitable perfusate consists of epoxy resin, red colorant, and curing reagent, and the optimal ratio is 12:3:5. The application of the method to the study of the effect of filtration time on the coal slime filter cake pores shows that the modified method is effective. At the initial stage of filtration, intergranular pores formed by coarse particles are the main pores. With increasing filtration time, the macropores formed by the coarse particles are mainly filled with fine particles, and the pore size of the filter cake rapidly decreases. These measuring results and rules are accurate. This method can be conveniently used to study the microstructure of filter cake, pore channel regulation, filtration dehydration mechanisms, etc. Full article

(This article belongs to the Special Issue Process Analysis and Carbon Emission of Mineral Separation Processes)

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17 pages, 5996 KiB

Open AccessTechnical Note

TBM Rapid Tunneling Roadway Support Parameters Design and Process Research

by Tao Hou, Zhonghui Xie, Ling Zhang, Guogang Cui, Ziwei Ding, Huafu Qiu and Yuhang Li

Processes 2023, 11(9), 2708; https://doi.org/10.3390/pr11092708 - 11 Sep 2023

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Abstract

Taking the specific production geological conditions of the auxiliary transportation lane in the west area of Gaojiabao coal mine of Shaanxi Zhengtong Coal Industry as the research background, based on the anchorage support theory and the characteristics of the TBM digging process, numerical [...] Read more.

Taking the specific production geological conditions of the auxiliary transportation lane in the west area of Gaojiabao coal mine of Shaanxi Zhengtong Coal Industry as the research background, based on the anchorage support theory and the characteristics of the TBM digging process, numerical simulation, theoretical analysis, and other research methods were used to investigate the depth of the destruction of the plastic zone of the surrounding rock of the roadway to form the reasonable support parameters of a large cross-section of hard rock roadway suitable for TBM digging and to propose an intelligent digging and support process of the TBM corresponding to the on-site practice. The proposed intelligent tunneling support technology corresponds to a field practice of TBM. The study shows that: combined with the field industrial test and adjusted by the peripheral rock deformation and damage law, the anchor diameter of 20 mm, the length of 2500 mm left-hand threaded steel anchors, row spacing of 1100 mm, spacing of 1200 mm, and the anchor diameter of Φ21.8 mm, the length of 6200 mm left-handed threaded steel anchors, row spacing of 1100 mm, spacing of 1200 mm are the most reasonable solutions, which can ensure the control of the tunnel peripheral rock. The program is the most economically efficient in ensuring the control of deformation of the roadway perimeter rock and maintaining normal use. Full article

(This article belongs to the Special Issue Process Analysis and Carbon Emission of Mineral Separation Processes)

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