Search Results (10)

Highly efficient flocculation and settling of tailings slurry is crucial for achieving high-concentration and low-cost backfill. Aiming to address the problem of the poor solid–liquid separation effect of superfine tailings slurry, this article improves its flocculation and settling effect by optimizing parameters. The flocculation and settling test was designed and carried out by the response surface method (RSM), with tailings slurry concentration (TSC), unit consumption of flocculant (UCF), and concentration of flocculant solution (CFS) as the influencing factors. The flocculation and settling effect was characterized by the underflow concentration (UC), settling velocity (SV), and mean chord length of floc (MCLF). A response surface regression model was established based on the test results to analyze the impact patterns of various factors and their interactions. Multi-objective optimization via the desirability function (DF) yielded optimal parameters: a TSC of 19%, a UCF of 16 g/t, and a CFS of 0.4%. Furthermore, experimental verification revealed that the relative error between the results and predicted values was within 3%. This indicates that optimizing flocculation and settling parameters has guiding significance for improving the thickening efficiency of superfine tailings, which will help optimize the tailings thickening process and reduce filling costs in mines. Full article

Advancements in mine tailings treatment technology have increased the use of superfine tailings, but their extremely fine particle size and high specific surface area limit the performance of superfine tailings cemented paste backfill (STCPB). This study investigates the effects of using superfine cement as a binder to enhance the fluidity, strength, and pore structure of STCPB. The influence of water film thickness (WFT) on STCPB performance is also examined. The results show that the cement-to-tailings ratio (CTR) and solid content (SC) significantly affect the spread diameter (SD) and unconfined compressive strength (UCS), following distinct linear/logarithmic and exponential trends, respectively. WFT has an exponential impact on SD and a non-linear effect on UCS, enhancing strength at low levels (0 μm < WFT < 0.0071 μm) and balancing hydration and flowability at moderate levels (0.0071 μm < WFT < 0.0193 μm) but reducing strength at high levels (WFT > 0.0193 μm). Additionally, superfine cement significantly improves the pore structure of STCPB by reducing porosity and macropore content. These findings provide valuable insights into optimizing STCPB for enhanced performance and sustainability in mine backfilling applications. Full article

The utilization of solid waste for filling mining presents substantial economic and environmental advantages, making it the primary focus of current filling mining technology development. To enhance the mechanical properties of superfine tailings cemented paste backfill (SCPB), this study conducted response surface methodology experiments to investigate the impact of various factors on the strength of SCPB, including the composite cementitious material, consisting of cement and slag powder, and the tailings’ grain size. Additionally, various microanalysis techniques were used to investigate the microstructure of SCPB and the development mechanisms of its hydration products. Furthermore, machine learning was utilized to predict the strength of SCPB under multi-factor effects. The findings reveal that the combined effect of slag powder dosage and slurry mass fraction has the most significant influence on strength, while the coupling effect of slurry mass fraction and underflow productivity has the lowest impact on strength. Moreover, SCPB with 20% slag powder has the highest amount of hydration products and the most complete structure. When compared to other commonly used prediction models, the long-short term memory neural network (LSTM) constructed in this study had the highest prediction accuracy for SCPB strength under multi-factor conditions, with root mean square error (RMSE), correlation coefficient (R), and variance account for (VAF) reaching 0.1396, 0.9131, and 81.8747, respectively. By optimizing the LSTM using the sparrow search algorithm (SSA), the RMSE, R, and VAF improved by 88.6%, 9.4%, and 21.9%, respectively. The research results can provide guidance for the efficient filling of superfine tailings. Full article

Previous studies have shown that the effectiveness of superfine tailings cemented paste backfill (SCPB) is influenced by multiple factors. To optimize the filling effect of superfine tailings, the effects of different factors on the fluidity, mechanical properties, and microstructure of SCPB were investigated. Before configuring the SCPB, the effect of cyclone operating parameters on the concentration and yield of superfine tailings was first investigated and the optimal cyclone operating parameters were obtained. The settling characteristics of superfine tailings under the optimum cyclone parameters were further analyzed, and the effect of the flocculant on its settling characteristics was shown in the block selection. Then the SCPB was prepared using cement and superfine tailings, and a series of experiments were carried out to investigate its working characteristics. The flow test results showed that the slump and slump flow of SCPB slurry decreased with increasing mass concentration, which was mainly because the higher the mass concentration, the higher the viscosity and yield stress of the slurry, and thus the worse its fluidity. The strength test results showed that the strength of SCPB was mainly affected by the curing temperature, curing time, mass concentration, and cement-sand ratio, among which the curing temperature had the most significant effect on the strength. The microscopic analysis of the block selection showed the mechanism of the effect of the curing temperature on the strength of SCPB, i.e., the curing temperature mainly affected the strength of SCPB by affecting the hydration reaction rate of SCPB. The slow hydration process of SCPB in a low temperature environment leads to fewer hydration products and a loose structure, which is the fundamental reason for the strength reduction of SCPB. The results of the study have some guiding significance for the efficient application of SCPB in alpine mines. Full article

The tailing paste thickening technology was investigated to achieve goaf reduction treatment and tailing resource utilization of metal mines and reach the effect of controlling two hazards with one waste. However, superfine tailing particles could easily form suspended water-locking flocs in the thickening process, which seriously affected the increase in the underflow concentration in the thickener. Undisturbed compression-stage bed samples were extracted using an in situ sampling method through a continuous dynamic thickening experiment. Then, the morphologies and geometrical structures of micropores were analyzed through high-precision computed tomography scanning. Subsequently, the influences of the shear evolution of pore structure and seepage channel on the dewaterability of underflow slurry were explored by combining Avizo software and 3D reconstruction technology. The thickening and dewatering mechanism of underflow slurry was also revealed. Results showed that under the shear action, the flocs were deformed and compacted, forming a high-concentration underflow. On this basis, the original micropores were extruded, deformed and segmented. Moreover, many loose micropores were formed, the connectivity became poor and the total porosity declined. The diameter of the water-conducting channel in the sample was enlarged because of the shear force and the seepage effect improved. The maximum flow velocity inside the pores was 1.537 μm/s, which was 5.49% higher than that under the non-shear state. Full article

Dealing with mineral tailings is one of the most important topics for solving the environmental problems in the mining industry. Among the techniques converting stacked molybdenum tailings to reusable cleaner products, one of the most effective ones is to use molybdenum tailings in concrete productions. The physical properties including density, microscopic structure and finesse module, and chemical composition of molybdenum tailings are similar with those of natural sand. The radionuclide assessment of molybdenum tailing meets the requirements for using as structural materials. Therefore, Molybdenum tailing is suitable to be used as the replacement of cement and fine aggregates in mortar and concrete. Based on the results of strength and duration performance comparison, the usage of molybdenum tailing as a replacement of natural sand is a more feasible way than that of ground super-fine molybdenum tailings in cement binder. It is feasible to use molybdenum tailings as fine aggregate in the preparation of structural concrete. When the amount of ground super-fine molybdenum tailings replacing cement is less than 10%, it is beneficial to improve the freeze-thaw and carbonization resistance of the concrete. Full article

Known for its advantages in preventing geological and environmental hazards, cemented paste backfill (CPB) has become a topic of interest for scientists and mining engineers in recent decades. This paper presents the results of a study on the use of cemented super-fine tailings backfill (CSUTB) in an underground mine for control of surface subsidence. An analytical solution is developed based on the available model to calculate the required strength of backfill when in contact with non-cemented tailings (NCT). The effect of solid contents on the rheological properties of CSUTB is investigated. A reasonable mix proportion (RMP) of CSUTB is determined for Zhongguan Iron Mine (ZGIM) based on laboratory experiments. The validity of RMP in surface subsidence control is verified by a 3D numerical model. The obtained results show that CSUTB requires higher strength when in contact with NCT than when in contact with orebody. Rheological characteristics, e.g., slump, fluidity, and bleeding rate of fresh CSUTB, decrease with higher solids content, of which values with a certain solids content can be determined by quadratic polynomial regression equations. RMP with a cement to tailings (c/t) ratio of 1:10 and a solids content of 70% is recommended for ZGIM, as it shows favorable mechanical and rheological abilities. The deformation parameters (curvature, inclination, and horizontal deformation rate) obtained from numerical modeling are acceptable and lower than critical values, meaning CSUTB can feasibly be used with RMP in subsidence control. Full article

This experimental study investigates the strength characteristics of cemented super-fine unclassified tailings backfill (CSUTB) and its failure mechanism. Physical and chemical properties of tailings from the Zhongguan Iron Mine (ZGIM) were tested. A series of uniaxial compressive strength (UCS) tests was conducted to determine the relationships between UCS of CSUTB and three factors of cement-tailings ratio (CTR), solid content and curing time. Gray relational analysis (GRA) method was then used to study the sensitivity of UCS to these three factors. Results indicate that ZGIM unclassified tailings is a kind of alkaline super-fine tailings with high activity and quality. UCS of CSUTB increases exponentially with the increase of CTR and solid content, and increases linearly with curing time. The curing time is the most important factor for the UCS of CSUTB, followed by CTR and solid content. The stress-strain curves obtained from UCS tests show the failure process of CSUTB, including four stages of initial deformation, linear elastic, yield deformation and complete failure. It is the result of damage evolution. Full article

In order to investigate the high volume fraction problem of the solid phase in superfine unclassified backfilling pipeline transportation, characteristic parameters were obtained by fitting to test data with an R–R particle size distribution function; then, a Euler dense-phase DPM (Discrete phase model) model was established by applying solid–liquid two-phase flow theory and the kinetic theory of granular flow (KTGF). The collision and friction of particles were imported by the UDF (User-define function) function, and the pipeline fluidization system, dominated by interphase drag forces, was analyzed. The best concentration and flow rate were finally obtained by comparing the results of the stress conditions, flow field characteristics, and the discrete phase distributions. It is revealed that reducing the concentration and flow rate could control pressure loss and pipe damage to a certain degree, while lower parameters show negative effects on the transportation integrity and backfilling strength. Indoor tests and field industrial tests verify the reliability of the results of the numerical simulations. Research shows that the model optimization method is versatile and practical for other, similar, complex flow field working conditions. Full article

The huge consumption of iron ores in China has attracted much attention to utilizing low grade complex iron resources, such as high-aluminum hematite-limonite ore, which is a refractory resource and difficult to upgrade by traditional physical concentration processes due to the superfine size and close dissemination of iron minerals with gangue minerals. An innovative technology for a high temperature reduction-magnetic separation process was studied to upgrade a high-aluminum iron ore assaying 41.92% Fe_total, 13.74% Al₂O₃ and 13.96% SiO₂. The optimized results show that the final metal iron powder, assaying 90.46% Fe_total, was manufactured at an overall iron recovery of 90.25% under conditions as follows: balling the high aluminum iron ore with 15% coal blended and at 0.3 basicity, reducing the dried pellets at 1350 °C for 25 min with a total C/Fe mass ratio of 1.0, grinding the reduced pellets up to 95%, passing at 0.074 mm and magnetically separating the ground product in a Davis Tube at a 0.10-T magnetic field intensity. The metal iron powder can be used as the burden for an electric arc furnace (EAF). Meanwhile, the nonmagnetic tailing is suitable to produce ceramic, which mainly consists of anorthite and corundum. An efficient way has been found to utilize high-aluminum iron resources. Full article