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Coal gasification fine slag is a kind of solid waste with low resource utilization rate. The complex embedding of residual carbon and inorganic minerals (ash materials) is the main reason restricting the efficient resource separation and utilization of residual carbon or ash materials. Hydrophobic-hydrophilic separation (HHS) is a separation technology in which mineral particles with different surface hydrophobicity values are enriched in the water phase and oil phase under the action of mechanical stirring. The water on the surface of hydrophobic particles is replaced by the oil phase to form flocs, which are enriched in the hydrophobic liquid phase, while hydrophilic particles are dispersed into the aqueous phase. In this study, the HHS process was used to separate the carbon/ash from the fine gasification slag produced by a Shenning gasifier, Texaco gasifier, and GSP gasifier of Ningxia Coal Industry Co., Ltd. The physicochemical properties of the original sample and the residual carbon products obtained by hydrophobic-hydrophilic separation were analyzed. The results show that HHS can separate the carbon/ash in the three kinds of fine slag to varying degrees. The carbon element is enriched into the hydrophobic phase to form the concentrates, while the silicon element, oxygen element, and metal element enter the tailings. The spherical ash with different particle sizes distributed on the surface of residual carbon and the gap of the matrix is basically removed, while the ash in the carbon-ash melt is difficult to remove. The ash contents of the concentrate and tailings of fine slag of the Shenning gasifier are 22.58 and 96.28%, respectively, which reach the best ash index compared with that of the other two gasifiers. From the change of mineral surface properties after HHS, the distribution of oxygen-containing groups, benzene rings, Si-O, and clay minerals or carbonate minerals in the three kinds of fine slag residual carbon products is basically similar. Compared with the other two gasifier products, the GSP gasifier concentrate has a larger specific surface area and less ash material, more amorphous carbon structures (less graphitic), and more active sites, resulting in a stronger combustion activity.

A method based on multiple images captured under different light sources at different incident angles was developed to recognize the coal density range in this study. The innovation is that two new images were constructed based on images captured under four single light sources. Reconstruction image 1 was constructed by fusing greyscale versions of the original images into one image, and Reconstruction image 2 was constructed based on the differences between the images captured under the different light sources. Subsequently, the four original images and two reconstructed images were input into the convolutional neural network AlexNet to recognize the density range in three cases: −1.5 (clean coal) and + 1.5 g/cm3 (non-clean coal); −1.8 (non-gangue) and + 1.8 g/cm3 (gangue); −1.5 (clean coal), 1.5–1.8 (middlings), and + 1.8 g/cm3 (gangue). The results show the following: (1) The reconstructed images, especially Reconstruction image 2, can effectively improve the recognition accuracy for the coal density range compared with images captured under single light source. (2) The recognition accuracies for gangue and non-gangue, clean coal and non-clean coal, and clean coal, middlings, and gangue reached 88.44%, 86.72% and 77.08%, respectively. (3) The recognition accuracy increases as the density moves further away from the boundary density.

Particle size distribution is extremely important in the coal preparation industry. It is traditionally analysed by a manual screening method, which is relatively time-consuming and cannot immediately guide production. In this paper, an image segmentation method for images of coal particles is proposed. It employs the watershed algorithm, k-nearest neighbour algorithm, and convex shell method to achieve preliminary segmentation, merge small pieces with large pieces, and split adhered particles, respectively. Comparing the automated segmentation using this method with manual segmentation, it is found that the results are comparable. The size distributions obtained by the automated and manual segmentation methods are nearly identical, and the standard deviation is less than 3%, indicating good reliability. This automated image segmentation method provides a new approach for rapidly analysing the size distribution of coal particles with size fractions defined according to consumer requirements.

Intelligent separation is a core technology in the transformation, upgradation, and high-quality development of coal. Realising the intelligent recognition and accurate classification of coal flotation froth is a key technology of intelligent separation. At present, the coal flotation process relies on artificial recognition of froth features for adjusting the reagent dosage. However, owing to the low accuracy and subjectivity of artificial recognition, some problems arise, such as reagent wastage and unqualified product quality. Thus, this paper proposes a new froth image classification method based on the maximal-relevance-minimal-redundancy (MR MR)-semi-supervised Gaussian mixture model (SSGMM) hybrid model for recognition of reagent dosage condition in the coal flotation process. First, the features of morphology, colour, and texture are extracted, and the optimal froth image features are screened out using the maximal-relevance-minimal-redundancy (MRMR) feature selection algorithm based on class information. Second, the traditional GMM clusterer is improved, called SSGMM, by introducing a small number of marked samples, the traditional GMM’ problems of unclear training goals, invisible clustering results, and artificially judged clustering results are solved. Then a new hybrid classification model is proposed by combining the MRMR with the modified GMM (SSGMM) which can be named as (MRMR - SSGMM). The optimal froth image features are screened by MRMR to provide the SSGMM classifier. In the process of training and learning the feature samples, using the marked feature samples of froth images to guide the unmarked feature samples. The information of marked feature samples of froth images is mapped to the unmarked feature samples, the classification of the froth images were realised. Finally, the accuracy of the SSGMM classifier is used as the evaluation criterion for the screened features by MRMR. By automatically executing the entire learning process to find the best number of froth image features and the optimal image features, so that the classifier achieves the maximum classification accuracy. Experimental results show that the proposed classification method achieves the best results in accuracy and time, compared with other benchmark classification methods. Application results show that the method can provide reliable guidance for the adjustment of the reagent dosage, realize the accurate and timely control of the reagent dosage, reduce the consumption of the reagent and the incidence of production accidents, and stabilize the product quality in the coal flotation production process.

Accurate classification and recognition of coal flotation froth is one of the key technologies for intelligent coal separation. At present, the coal flotation process relies on artificial recognition of froth features for adjusting the reagent dosage, which cannot realize the optimal control of the quality of the clean coal product and the cost of the reagents. Therefore, in this paper, it is proposed a method of froth image clustering with feature semi-supervision through selection and label information. It is mainly divided into two stages: offline clustering and online recognition. The offline stage is to preprocess the froth image under various reagent conditions, extract the morphology, colour and texture features, and select the multi-dimensional optimal froth image features. A small number of marked samples are introduced to optimize the Gaussian mixture model. The selected optimal features are integrated into the optimized Gaussian mixture model to construct a froth image clusterer with multi-dimensional optimal features and class labels. In the online stage, the real-time froth image features are input clusterer and compared with the cluster feature samples to identify the current reagents conditions, which is used as feedback information to guide the abnormal reagent conditions during the production process. The effect of the amount of supervision information and the quality of feature on clustering results is analyzed and compared through experiments. The application results show that this method can provide key technical support for the accurate control of the dosage of reagents and the quality of clean coal product in the coal flotation production process, reduce the cost of reagents and the number of production accidents, improve the economic benefits, and promote the development of coal flotation intelligence to a higher level.

As the reserves of high-quality coal resources in China are decreasing, it is imperative to improve the processing and comprehensive utilization of low-rank coal. In this study, NaNO

In view of the similarity between the partition curve of coal preparation and the cumulative curve of distribution function, the quartile of random distribution is often used to describe the charac...

In coal mines, process management is related with planning and flow of coal minerals from their mining points to journey’s end. The process is dependent on the operational decisions, which should be completed during coal production. In these systems, simulation modelling is assumed a powerful tool for decision making. The simulation modelling can further be enhanced through applying artificial intelligence (AI) and machine learning (ML) methods. The communication of water with clay minerals upholds the water adsorption on the clay surface, which makes them complex systems. Therefore, evading the water absorption from the clay turns out to be a hard job. The computational trainings of clay minerals are needed to comprehend the dynamics of water distribution. Tradition of coal slurry treatment is completed by adding medicament of its mineral flocculation sedimentation. As a result of coal, slime water contains a lot of clay minerals that are rich in kaolinite versatility and it is difficult to settle. The flotation will be one of the kaolinite recycling. In this paper, clay minerals containing a variety of minerals were taken as samples, and sodium dodecyl sulfate and sodium oleate were used as collectors to explore the flotation effect through test and molecular dynamics simulation. A machine learning based intelligent decision support system is designed to improve the outputs of the simulation model. The results show that when the pH value is 8 and the amount of collector and sec-octanol are 150 g/t and 250 g/t, respectively, the flotation rate of fine mineral can reach 63.25%. According to the molecular dynamics simulation results, the addition of the collector can reduce the hydrophilicity of the kaolinite surface, and the physical adsorption of SDS only occurs on the (001) surface.

To study the effects of ethylene oxide (EO) number in surfactants on low rank coal (LRC) flotation, dodecyl ethoxyl ethers (C12EOn) with three different EO numbers were selected and their adsorption and flotation behaviors were experimentally investigated. The results show that all C12EOn can obtain the same maximum flotation recovery. Increasing the number of EO in C12EOn lowers the necessary amount of reagent. Greater selectivity can be achieved with increasing EO number in C12EOn. Furthermore, the surface model of LRC (organic matter) and kaolinite (representative of mineral matter) was constructed, and the adsorption behavior of C12EOn on the LRC surface was analyzed based on the adsorption configuration, interaction energy, hydrogen bond interaction and surface areas. The calculated results show that increasing the EO number in C12EOn could accelerate the interaction between LRC and C12EOn at low surfactant concentrations. Since the same chemical structure of C12EOn, increasing the EO number does not make any significant difference in their interaction when the surfactant concentration is high. A combined theoretical approach [density functional theory (DFT) calculations and molecular dynamics simulations (MD)] was adopted to investigate the microscopic mechanism of the increase in LRC hydrophobicity by C12EOn adsorption. Finally, the competitive adsorption of C12EOn between organic matter and kaolinite was studied. The research results indicate that the selectivity is higher with increasing EO number in C12EOn, which is consistent with the experimental results. The microscopic mechanism of EO groups in surfactants on LRC flotation discussed in this study may have potential use in surfactant design and selection.

Decrease in hydrophilicity of lignite and moisture readsorption after adsorption of a series of lauryl polyoxyethylene ether (C12(EO)n) were studied with the measurement of wetting heat and moisture readsorption ratio. Effect of the hydrophilic lipophilic balance (HLB) of C12(EO)n on efficiency of the decrease in lignite hydrophilicity was investigated. X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption/desorption were used to disclose the coverage characteristics of the different functional groups and the aggregations in pores of lignite by the adsorbed surfactant. Results indicated that both wetting heat and moisture readsorption ratio of lignite decreased significantly using different C12(EO)n. The size order of wetting heat of lignite after adsorption of different C12(EO)n with variation of the HLB values were almost consistent with that of moisture readsorption. The low HLB values of C12(EO)n especially with HLB of around 13.62 and 12.49/9.75 are most efficient respectively for the decrease in wetting heat and moisture readsorption of lignite. Coverage of oxygen-containing groups by surfactant was mainly devoted to the decrease in hydrophilicity of lignite. Among those oxygen groups in lignite surface, the COO/COOH and C-O/OH were responsible for adsorption priorities. Aggregations of surfactant in pores were beneficial for decreasing moisture readsorpiton of lignite surface due to the decreased storing space of moisture.

The rapid determination of coal ash content is of substantial significance in coal preparation plants. A new ash content prediction method that is based on images of multiple ring light sources with various incident angles is proposed in this paper. Diffuse and specular reflections were separated based on image brightness in a single light source, and the intersections of these regions in multiple light sources were calculated to increase the monotonicity of the relationship between the image brightness after classification and the ash content. Then, an ash content prediction model was established by using the Logistic deformation function Ash = a 1 + e ( - b ∗ x - c ) + f to fit the relationship between the variables that were extracted from the images and the ash content. Then, the average of the preliminarily predicted ash content values was calculated to obtain the final predicted ash content. The ash content values of coal samples from four mines were predicted via this method, and the maximum root mean square error of the predicted ash content with respect to the actual ash content was 1.25%; hence, the prediction method realized high accuracy in ash prediction.

In coal beneficiation, the clean coal would be easily contaminated with the super fine montmorillonite particles coating on it. This interaction between coal (hydrophobic) and montmorillonite (hydrophilic) surfaces is the interactions between the asymmetric systems. Previous studies detected the force between the montmorillonite and graphite or between the montmorillonite mounted tip and coal substrate to represent the interactions between 001 surface and coal. However, there is still lack of experimental direct measurement on the interaction between montmorillonite 001 surface and coal macerals. In this study, proposes methods for determinine the interactions between coal macerals and 001 surface of Na-, K- and Ca- montmorillonite directly by using an atomic force microscope (AFM). The results indicate that the 001 surface of Na- and Ca- montmorillonite served as the chaotropic and kosmotropic surface when it is adjacent to coal surfaces, with an attractive force and repulsive force occurring between them, respectively. The 001 surface of K-montmorillonite served as the chaotropic surface and kosmotropic surface while it is close to liptinite and inertinite, respectively. This chaotropic or kosmotropic property of the surface is determined by the coordination number of the cations and wettability of the hydrophobic surface simultaneously.

The wettability changes of lignite after adsorption of cetyltrimethylammonium bromide (CTAB) were studied with the aim of disclosing the contributions of particle size and mineral matter. The adsorptions of CTAB from aqueous solution onto lignite samples with different particle sizes and pure mineral matter (kaolinite, calcite, and quartz) were investigated. Changes in hydrophilicity of samples were evaluated by wetting heat with different reagents using a microcalorimeter. It was observed that the wetting heat of lignite wetted by water was much higher than that wetted by alkanes. The hydrophilicity of lignite decreased significantly after adsorption of CTAB, and the hydrophobicity subsequently enhanced. Though adsorption density of CTAB on lignite surface increased with the diminishment of particle size, the efficiency of hydrophobicity enhancement decreased. In addition, the results of wetting heat suggested that organic content of lignite played a dominant role for the hydrophilicity properties of lignite. Adsorption of CTAB not only decreased the hydrophilicity of organic content but also that of mineral matter. The effect of mineral matter on the hydrophilicity modification of lignite by CTAB depended on its species. Kaolinite and calcite had more intensity for hydrophilicity modification by adsorption of CTAB than that of quartz.

The interactions in the “lignite-surfactant” system were studied with the aim of disclosing the mechanism of the decrease in hydrophilicity of lignite using cetyltrimethylammonium bromide (CTAB). The inhibiting efficiency in the hydrophilicity of lignite by CTAB was studied by measuring the wetting heat using a Calvet calorimeter. The adsorption of CTAB to organic content and mineral matter was analyzed, and the relationship between the distribution characteristics of different functional groups and the inhibiting efficiency in hydrophilicity was discussed. The hydrophilicity of lignite was decreased significantly after adsorption of CTAB. CTAB decreased the hydrophilicity more effectively for a more strongly hydrophilic sorbate, and an excess adsorption was not beneficial. Competitive adsorption existed between the oxygen-containing groups and the silicon-containing mineral matter of lignite, and the adsorption to oxygen-containing groups occurred prior to reaching the mineral matter surface. The decrease in hydrophilicity of lignite by CTAB was shown to be closely associated with the distribution characteristics of the adsorbed layer. Coverage of the oxygen-containing groups by a directed surfactant layer was mainly devoted to the decrease in the wetting heat of lignite. Among these oxygen-containing groups, the COO/COOH group of lignite played a key role in the decrease of hydrophilicity due to its high adsorption capacity for CTAB.

Interfacial water at the low-rank coal (LRC) surface plays an important role in many technological processes, including flotation, slime water settling and dewatering. In this work, molecular dynamics simulations were performed for a series of model systems consisting of a model surface of Wender lignite and 100–600 adsorbed water molecules. A number of equilibrium properties, including density profiles, radial distribution functions (RDFs) and binding energies, are reported to explain the characteristics of interfacial water. The RDF results demonstrate that the order degree of the water molecules decreased with increasing distance from the LRC surface, although the structure of interfacial water at the LRC surface is substantially similar to that in bulk water. In addition, the results also present that the four groups affecting interfacial water at the LRC surface follow the order of carboxyl > hydroxyl ≫ ether > carbon chain. The density profiles of water molecules are insufficient to give a description of interfacial water in detail, but it can be speculated from the density profiles and RDFs that water molecule adsorption at the LRC surface is preferentially fixed around the polar functional groups when there are fewer water molecules. With increasing number of water molecules, water gathers at the hollows. Finally, the water molecules cover the whole surface of the LRC. The calculated binding energies increase monotonically with increasing number of water molecules, while the unit binding energies show the opposite trend. Furthermore, a common non-ionic surfactant, dodecyl 7-ethoxyl ether (C12EO7), was selected to modify the LRC surface. The hydrogen bonding, density profile and binding energy are reported to provide a microscopic understanding of the behaviour of interfacial water before and after surfactant adsorption. The results indicate that surfactant adsorption reduces the difference between interfacial water and bulk water. The simulation results are in accordance with the available experimental data.

Physicochemical Problems of Mineral Processing; ISSN 2084-4735

The settlement of particles is of great importance in many areas. The accurate determination of drag coefficient and settling velocity in wide Reynolds number (Re) range remains a problem. In this paper, a series of new formulas for drag coefficient of spherical particles based on theoretical laws, such as the Stokes law, the Oseen law, and the Goldstein law, were developed and fitted using 480 groups of experimental data (Re

Normalized mathematical models with 4 or 5 parameters were developed to characterize distribution (Tromp) curves based on the Edgeworth-Kapteyn generalized normal distribution. The basic structure of g(x) that is in the Edgeworth-Kapteyn generalized normal distribution was the power function's rational expression. The models were found to be satisfactory for three groups of a dense-medium cyclone distribution data and five groups of a water-only cyclone distribution data, and, in most cases, they were preferred over the arctangent model and the modified hyperbolic tangent model.

Effects of the air injection into a water-only cyclone on the separation performance of the cyclone treating coal in the 1 × 0 mm particle size range were investigated. The results showed that by using air injection the water-only cyclone had a good density separation for the +0.125 mm size fraction and minimized the effects of the particle size. When the gas-liquid ratio increased, the density cut-point decreased, as did the Ecart probable (Ep) value, which could be reduced to 0.05 for the +0.5 mm size fraction. Therefore, the density cut-point of a water-only cyclone can be adjusted in real time by changing the gas-liquid ratio to meet variable market requirements.

In order to discharge the slime with high ash content and thus decrease the middling cycling of column flotation, a classification device was designed employing the principle of natural settling of the particles. Good classification was obtained and more than half of the high ash slime can be discharged as the overflow. A mathematical model was introduced to simulate the partition function with the fish-hook appeared in the experiment results. The model involves a Weibull function and a Gauss function representing the classification and the entrainment, respectively. The fitting results show a good agreement with the experimental results. Some parameters can be significantly related to the operating conditions. Based on these relationships, a comprehensive multi-variant model was established and showed good fitness. The relationships embodied in the comprehensive model are coincident with the traditional classification and settlement theory.

this paper research on spatial information service laws of development and application from angle of model and put forward the basic conception of spatial information service model basing on information service model. It presents a complete structure of model, and detailedly explains elements, the main characteristics and principles of interaction. Consider that the reciprocity between the various elements is the main inner factor which can produce a variety of different services type, and thus lead to different spatial information services with a variety of different forms. At last this paper accord to the relationship between the inner factor and elements to bring forward the abstract services classification results which currently can cover almost all the spatial information service types, and give theoretical support.

This paper presents a new method to describe the relationship between services, which refers to the basic concepts of geometric topology. It uses the relationships between points and lines to describe that from input and output information flow in the service, further to produce a static invoking relationship between services. According to this abstract relationship between the points and lines of the spatial information service, it can generate a valid topological relationship between the services with point elements, line elements and topology relationship tables. The topological relationship between services can put into one-to-one relationship with information processing each process, and thus can improve the speed and performing efficiency of the service combination and matching. This article defines a concept of the point elements and line elements in the service topology, describes the properties of the elements, sets up four kinds of topological relationships and their corresponding information process. A proposal of the method of establishing topological service description is provided. Ultimately there are specific examples to represent the construction process of services topological relationships and their final results.