Mining Science and Technology (China)最新文献

Bio-leaching of pyrite by native strains of acidophilic bacteria was examined by laboratory scale tests. Three groups of batch trials in agitated flasks and three continuous column leaching tests were performed. The leaching ability and efficiency of native bacteria was greatly improved by adaptation of the bacteria to the test conditions. These cultivated bacteria were then used for the leaching process. The changes in solution pH, Eh, Fe²⁺ concentration, and sulfate ion concentration were monitored throughout the tests. A portion of the pyritic sulfur is transformed into soluble sulfate ion. The desulfurization ratio of 42.6% was obtained in a flask shaking test and a ratio of 39.4% was obtained during column leaching. A weight gain test was performed on leached and unleached samples by exposing the samples to humid air for several days. A smaller weight gain of the bio-leached samples indicates that removing sulfur from the sulphide ore helps reduce its oxidation rate and the potential for spontaneous combustion.

Deep coal mines in northern Anhui province, China, provide opportunities for tracing the distribution and fractionation of rare earth elements (REEs) in deep seated environments. Major ions, as well as REE concentrations were measured in groundwater from a sandstone aquifer located between –400 and –280 m. Our results indicate that this groundwater consists of Cl·HCO₃-Na or Cl·CO₃-Na water types with warm temperature (30.1–31.4 °C), circumneutral pH (7.27–8.61) and high levels of total dissolved solids (TDS = 1306–2165 mg/L). Concentrations of REEs in groundwater are high as expressed by their Nd concentrations (0.0086–0.018 μg/L). Except for weak heavy REEs (HREE) enrichment relative to light REEs (LREE), the similarity of REE distribution patterns between groundwater and aquifer rock indicate that enrichment of REEs is considered to be controlled by aquifer rock, as well as by their minerals, whereas the fractionation of REEs is controlled by HREE enriched minerals and, to a lesser extent, by inorganic REE complexes. Ce anomalies normalized to Post Archean Average Shale (PAAS) and aquifer rock are weak, which probably reflect the contribution of reduced conditions in combination with pH, rather than a signature of aquifer rock.

We proved theoretically that geodetic height, measured with Global Positioning System (GPS), can be applied directly to monitor coal mine subsidence. Based on a Support Vector Machine (SVM) model, we built a regional geoid model with a Gaussian Radial Basis Function (RBF) and the technical scheme for GPS coal mine subsidence monitoring is presented to provide subsidence information for updating the regional Digital Elevation Model (DEM). The theory proposed was applied to monitor mining subsidence in an Inner Mongolia coal mine in China. The scheme established an accurate GPS reference network and a comprehensive leveling conjunction provided the normal height of all GPS control points. According to the case study, the SVM model to establish geoid-model is better than a polynomial fit or a Genetic Algorithm based Back Propagation (GA-BP) neural network. GPS-RTK measurements of coal mine subsidence information can be quickly acquired for updating the DEM.

We studied the geochemical characteristics of illite clay rocks and their importance from the Shihezi Formation of Late Permian in the Hanxing mining area by means of ICP-MS and sequential X-ray fluorescence spectrometry. The results show that the amount of SiO₂ is between 53.37% and 61.58% (by weight) and that of Al₂O₃ 22.40% and 31.31% (by weight). The ratio of SiO₂/Al₂O₃ lies between 1.71 and 2.75. The amount of K₂O ranges from 1.11% to 2.56% (by weight). The amounts of Fe and Ti are higher than the theoretical values in illite clay rock would indicate. The amounts of some trace elements, such as Ga, As, Ba, Cu, Th and U are higher than their Clark values, while that of another 23 trace elements are found to be close to their Clark values. The amounts of REE range from 22.59 to 570.54 μg/g, with an average of 163.23 μg/g. The ratios of LREE/HREE range from 5.41 to 21.82, with an average of 8.87. These characteristics show that LREE are much richer in content than HREE. The REE distribution patterns of our samples were characterized by clearly negative Ce and Eu anomalies. We analyzed the sedimentary environment of the Hanxing mining area in Late Permian by the characteristic element ratio method. The ratios of Mn/Fe range from 0 to 0.0168, which are lower than those in a marine sedimentary environment. The ratios of Sr/Ba (0.20–0.41) are less than 1. These are all indications that the sediments of the Hanxing mining area in Late Permian form largely a continental sedimentary environment. The sedimentary water is freshwater, a conclusion reached on the basis of the ratios of Th/U (2.66–6.62) and of Ca/(Ca + Fe) (0.01–0.059); the average ratio of Fe²⁺/Fe³⁺ is 4.8. The sedimentary water condition is weakly acidic and weakly oxidative-weakly reductive, a conclusion reached on the basis of ratios of Fe²⁺/Fe³⁺ (4.8) and of Ce_anom (−0.08).

In order to discuss the geochemical characteristic of REEs (rare earth elements) and their geological application, we measured the contents of rare earth elements, trace elements and minerals of 29 Lopingian (Late Permian) mudstone samples in Panxian county, carrying out ICP-MS and XRD analysis. The results show that the amount of REEs (185.56–729.46 × 10⁻⁶) is high. The ratios of w(LREE)/w(HREE) (6.84–13.86) and w(La)_N/w(Yb)_N (1.01–3.02) show clear differentiation of LREEs and HREEs. ΣREE has a significantly or critically positive correlation with lithophile elements Th, Nb, Ta, Ti, Ga, Sc, Cs, Zr, Hf, Sr, Be and chalcophile element Zn, a critically negative correlation with siderophile element Fe and a slightly positive correlation with illite, illite smectite mixed layers and siderite. REEs originate mainly from terrigenous minerals, in an inorganic phase. Source rocks of our samples consist of Emeishan basalt and a small part of sedimentary rocks, as suggested by the distribution patterns of REEs and w(∑REE)–w(La)/w(Yb) diagram. Moreover, abnormal surfaces near the sequence boundaries (SB2, SB3, SB4) are related with the boundaries, identified by geochemical characteristics of the REEs, such as ∑REE, w(LREE)/w(HREE), Eu/Eu^∗ and Ce_anom.

The role of Ni(NO₃)₂ in the preparation of a magnetic activated carbon is reported in this paper. Magnetic coal-based activated carbons (MCAC) were prepared from Taixi anthracite with low ash content in the presence of Ni(NO₃)₂. The MCAC materials were characterized by a vibrating sample magnetometer (VSM), X-ray diffraction (XRD), a scanning electric microscope (SEM), and by N₂ adsorption. The cylindrical precursors and derived char were also subjected to thermogravimetric analysis to compare their behavior of weight losses during carbonization. The results show that MCAC has a larger surface area (1074 m²/g) and a higher pore volume (0.5792 cm³/g) with enhanced mesopore ratio (by about 10%). It also has a high saturation magnetization (1.6749 emu/g) and low coercivity (43.26 Oe), which allows the material to be magnetically separated. The MCAC is easily magnetized because the nickel salt is converted into Ni during carbonization and activation. Metallic Ni has a strong magnetism on account of electrostatic interaction. Added Ni(NO₃)₂ catalyzes the carbonization and activation process by accelerating burn off of the carbon, which contributes to the development of mesopores and macropores in the activated carbon.

In order to compensate for the deficiency of present methods of monitoring plane displacement in similarity model tests, such as inadequate real-time monitoring and more manual intervention, an effective monitoring method was proposed in this study, and the major steps of the monitoring method include: firstly, time-series images of the similarity model in the test were obtained by a camera, and secondly, measuring points marked as artificial targets were automatically tracked and recognized from time-series images. Finally, the real-time plane displacement field was calculated by the fixed magnification between objects and images under the specific conditions. And then the application device of the method was designed and tested. At the same time, a sub-pixel location method and a distortion error model were used to improve the measuring accuracy. The results indicate that this method may record the entire test, especially the detailed non-uniform deformation and sudden deformation. Compared with traditional methods this method has a number of advantages, such as greater measurement accuracy and reliability, less manual intervention, higher automation, strong practical properties, much more measurement information and so on.

In order to monitor dangerous areas in coal mines automatically, we propose to detect helmets from underground coal mine videos for detecting miners. This method can overcome the impact of similarity between the targets and their background. We constructed standard images of helmets, extracted four directional features, modeled the distribution of these features using a Gaussian function and separated local images of frames into helmet and non-helmet classes. Out experimental results show that this method can detect helmets effectively. The detection rate was 83.7%.

Coal accounts for about 70% of the primary energy sources in China. The environmental pollution and resources waste involved with coal processing and utilization are serious. It is therefore urgent to develop highly-efficient coal resources utilization theory and methods with low-carbon discharge. Based on our long-term basic research and technology development, the progress in beneficiation, cleaning, and transformation of coal, which includes dense phase fluidized bed dry beneficiation, deep screening of wet fine coal, micro-bubble flotation column separation, molecular coal chemistry, and transformation and separation of coal and its derivatives into value-added chemicals under mild conditions, is discussed.