نشریه مهندسی منابع معدنی
سال پنجم شماره 4 (زمستان 1399)

Independent component analysis (ICA) is a relatively new multivariable statistical method originally devised for the blind source separation (BSS) problem, where there is no information on how to mix primary sources (mixed signals) and only the necessary condition is independence of the primary signals. Hence, ICA can be used in mineral potential modeling where several independent mineralization processes result in observed variables such as geophysical and geochemical information, and we do not know how the geophysical and geochemical effects of different mineralization processes are mixed together. In this study, we tried to introduce the ICA method as a knowledge-driven method of mineral potential modeling. To this end, an area of 4800 square kilometers in south of Neyshabur, northeast of Iran, was investigated to map the mineral potential of podiform chromite deposits. In this regard, geochemical stream sediment sampling data, ophiolitic facies map, structural pattern of fractures and serpentinite alteration location in the region were used for this study. Finally, the results of mineral potential modeling by the ICA method were compared with the results of univariate and multivariate geochemical studies and were also validated by using locations of the known mineral prospects in the region and receiver operating characteristic (ROC) method. As a result, the area under the ROC curve was marked by 0.967, indicating the outstanding performance of the ICA modeling.

In recent years, the use of micro X-Ray images with very high resolution (as low as 100 nm) in different scientific fields has led to the development of modern methods for performing various calculations and measurements. The use of these images has become quite popular among petroleum engineers. This is because the reservoir rock-related properties like petrophysical properties and the properties that are simultaneously related to reservoir rock and fluid such as drainage and imbibition phenomena can be estimated using micro X-Ray images. To estimate these properties, some geometrical properties of grainsof two different cores are calculated and compared to each other through micro X-Ray images and somesoftware. Then, with the help of the micro X-Ray images, the necessary information for simulation of thepore network of the rock is gathered. Afterward, with the use of this information and some other software, the pore network of each of these rocks is simulated and consequently, the porosity and permeability of each of these rocks are estimated. In the simulation process, some assumptions are made to prevent the complexity of the calculations. These assumptions result in a deviation of the calculated values from real (laboratory) values. Therefore, using the calculated geometrical values obtained in the first step, a relationship is achieved by which the calculated values of the simulation are brought closer to those of the laboratory. In this research, based on the aforementioned steps and by using the sphericity, convexity, and aspect ratio of grains obtained from 2D images, a correlation is developed. Ultimately, the estimated rock properties procured by simulation are related to measured laboratory data through this correlation.

Mining is impossible without employing labor. The production and extraction of minerals require a combination of labor, machinery and energy. In this paper, through a review of the stylized facts of the Iranian mines under operation, first the factors affecting labor productivity are identified, and then, by specifying an econometric model, their effects on productivity are estimated over the period 1983-2017. Given the non-stationary variables, the Johansen-Juselius co-integration test confirms the existence of a long-term relationship among the variables. Accordingly, the share of skilled labor, private ownership of mines, capital-labour ratio, and wages and salaries positively influence labor productivity. According to the findings, designing a payment and reward system related to the added value of employees, using labor-saving technologies (advanced mining equipment) in the extraction of deep and high-risk mines, privatization of non-strategic mines, increasing the share of the labour force in the profit and sale of minerals, paying attention to the substitution and complement inputs (labor, energy and capital) in mineral extraction and processing are recommended to increase labor productivity in mines.

Evaluation of TBM performance is very important in estimating the cost and time of a tunnel project. Sensitivity analysis of a model is performed to examine the influence of the input variables on the output variables. In this study, results variability of main models of TBM penetration rate (PR) prediction have been investigated based on the geological and field performance data at Lar-Kalan water conveyance tunnel. The overall results indicate that increase of thrust force, CLI, RPM, porosity, and fracturing factor and the decrease of Q value, quartz content, unconfined compressive strength, tensile strength, induced biaxial stress on tunnel face, and RQD increases the PR. Sensitivity analysis has been evaluated on the basis of the two Tornado and Spider charts for different models, and the effect of the input parameters variation on the variation of the PR have been investigated and the parameters that have the greatest influence on the PR were specified. Among the geological conditions, the variation of the Q value, porosity, UCS, RQD and among the machine parameters, variation of the thrust force and RPM have the greatest impact on the variation of the penetration rate in the project.

In this paper, the failure pattern of non-persistent joint under U shape cutter was studied by experimental test and numerical simulation. For this purpose, 4 gypsum sample with dimension of 5cm*10cm*10cm containing perpendicular non-persistent joint were prepared.  Samples have 2 vertical non-persistent joint with lengths of 1cm and 2 cm. the angle of small joint related to horizontal axis was 0°, 45°, 90° and 135°. This sample was subjected to U shape cutter loading. Concurrent with experimental test, numerical simulation was performed using Franc2d on the non-persistent joint. Totally 12 numerical model was built that some of them have similar configuration with experimental specimens. The results show that perpendicular non-persistent joint configuration has important effect on the failure pattern.  The compressive strengths have minimum value when small joint angle were 45° and 135°. The comparison between experimental results and numerical output shows that the good accordance was established between experimental tests and numerical simulation.

In the concentration plant of Hamadan, magnetite concentrate is produced by low intensity magnetic separators (LIMS). As a result, 47% of feed sulfur was recovered in magnetite concentrate, keeping sulfur at higher content than that is commercially desired. Mineralogical investigations revealed that Pyrrhotite and Pyrite are the most abundant sulfur minerals, respectively. Davis Tube investigations indicated that by decreasing magnetic field intensity and particles size, sulfur content  in magnetite concentrate could be decreased to 1.7%,  which is still much more than desired.  Further investigations were performed using flotation method and based on statistical design. Modelling and analysis of design data revealed that the dosage of collector and activator and their interaction have statistically significant effects on the process with 95% confidence level. İt was found that the optimum condition of removing sulfur would be achieved using 1100 g/t of Potassium amyl xanthate (collector), 200 g/t of copper sulfate (activator), 65 of g/t MIBC and 65 g/t of A65 (frothers), at pH=6 and solid percent of 45%. At the given condition, 98% of sulfur in magnetite concentrate (2.3% sulfur) was successfully removed and the product with 0.04% sulfur was obtained.

About 40 percent of total raw coal feeding to Tabas coal preparation plant, consists of particles in the size range of -50+6 mm. These particles are washed in a 700 mm (diameter) two-stage Tri-Flo dense medium separator. In order to understand the mechanism of separation, a laboratory setup including a transparent 70 mm Tri-Flo separator, tanks, pumps and the required instrumnets was designed and manufactured. In laboratory studies, some polymeric colorful tracers were added to the separator with different air core sizes, and were captured and counted in products’ tanks. The results indicate that probable error of separation (Ep) decreases while air core gets bigger. Relying the findings of laboratory studies, the industrial Tri-Flo was optimizaed using density tracers in the specific gravity range of 1.20 – 2.20 g/cm3, when the separator was treating raw coal. In this phase, we tried to change dense medium flow rate and internal tube diameter in the meaningful levels to evaluate the separator performance, rapidly. An increase of 9% in the production yield and 0.5% increase in clean coal ash were the results of increasing the internal tube diameter in industrial separator from 205 mm to 235 mm. 3% increase in the production yield and 1% decrease in the clean coal ash was also observed with increasing the medium flow rate. Similar to the results observed in laboratory separator, increasing the flow rate and pipe diameter leads to clearer separation in industrial separator. This research presents a successful use of the laboratory results for optimization of an industrial separator.

One of the challenges in the rare earth elements (REE) production industry is the difficulty of separating them from each other. Therefore, in the present study, the possibility of cerium separation from carbonate concentrate of REEs containing 22.75% Ce, 9.4% La and 8.6% Nd (total REEs of 41.51%) was investigated. Two methods were used to separate Ce from other REEs. In the first method, due to the very low solubility of Ce4+, the calcination of carbonate concentrate and conversion of cerium carbonate to cerium oxide and selective dissolution of other REEs from the calcine were investigated. In the second method, prior to the carbonate precipitation of REEs, the possibility of cerium oxidation in the sulfate solution (by using potassium permanganate) and its subsequent selective separation from other REEs was investigated. Results of the calcination (first method) showed that only 35 and 45% of La and Nd were dissolved at 80⁰C after 2 hours leaching with 1 molar nitric acid, respectively. Results of the calcine leaching with 4 molar nitric acid at 80⁰C for 2 hours showed that more than 90% of the La and Nd were dissolved. In this conditions, 35% of the Ce was also dissolved and the leaching process was not selective. In the second method, using potassium permanganate with a stoichiometric ratio of 1.5 to 1 for oxidant to Ce, pH 3.5 for 1 hour, 98% of the Ce and less than 1% of La and Nd were precipitated. The resulting hydroxide was calcined at 850⁰C for 1 h to produce CeO2 and finally a Ce oxide concentrate was obtained with 99% purity.