فصلنامه مهندسی معدن
پیاپی 3 (بهار 1386)

In this article at first NTH and CSM utilization factor prediction models as topics of the empirical and the theory-empirical models are reviewed. Then with notice to structure of the data bank that is used for prediction of utilization, effective parameters on utilization are introduced. With use of two and multi variable statistical analysis some relations are presented for prediction of utilization and on results obtained from theses relations are discussed. In flow with use of Neuro Network the most suitable Network for prediction of utilization is determined and ability of this network in comparison with multi variable statistical analysis and real value of utilization factor is investigated. Prediction of utilization for Gavoshan Tunnel's TBM with Neuro Network is discussed in the latest parts of article.

In this paper, beneficiation studies of Moundon phosphate ore were investigated for reduction of its gangue minerals such as carbonates and iron minerals. According to the mineralogical studies, phosphate mineral content of the ore (collophane) was sedimentary mineral and the predominant constituents of the gangues were calcite and quartz. Experimental designs were performed using Taguchi method for leaching and calcination experiments. To remove the carbonate gangue and to increase the P2O5 content, leaching experiments were performed using acetic acid. The effect of different parameters such as leaching time, acetic acid amount and solid/liquid ratio were investigated. In the optimum conditions the residue of the leaching experiment contained 31.19% P2O5 with 99.9% recovery. Calcinations method was employed to decrease the carbonate gangue and increase the P2O5 content. Results showed that under the optimum conditions the calcine contained 25.25% P2O5 and the recovery was 99.8%. Also the wet high intensity magnetic separation method was used to reduce the amount of Fe2O3 in the ore. Under the optimum conditions, the amount of Fe2O3 was decreased from 2.58 to 1.43%.

In feasibility studies, several techno-economical aspects are reviewed. Cost items have a considerable role on range of variation of project outputs and analysis of distribution of their relative share is necessary. Economical and financial evaluation is on the basis of assumptions and variables which are estimated under uncertainty conditions and therefore, sensitivity and risk analysis of project economical out put should be evaluated. In this research, with the help of Excel and Comfar software, for economical and financial analysis of Sungun copper mine, a model was developed and run considering scenarios for a certain variation of expected value of critical variables. On the basis of cost analysis results, mill plant and mine have the greatest share of capital cost with 41% and 32%, respectively. From operating costs point of view, mill plant (52%) and mine (34%) also have the greatest share. Also it was observed that internal rate of return (IRR) is affected more by concentrate price comparing to other relevant factors. In this regard, mill recovery plant, exchange rate, capital costs, mine overall slope angle and operational costs can be considered in the next degrees of importance. Finally, according to risk analysis, it was concluded that with a 90% level of confidence, range of range of IRR is more than 9.32% and less than 19.56%.

Leaching is one the stages of hydrometallurgy which is usually applied for uranium ore processing. Uranium ores are normally leached using acidic or alkaline solutions, such as H2SO4 or Na2CO3. Khashoomi region is located in 150km southeast of Yazd city. During primarily exploration stage in Khashoomi 47 anomalies were recognized from which, anomaly 6 is the most important and promising one. In this research project the sample from Khashoomi deposit was studied using acid leaching method, to optimize significant parameters levels in process, such as size of particles, acid (H2SO4) consumption, type and consumption of oxidant, temperature, leaching time, and solid percent of pulp. Different experiments were carried out and the optimized values for above parameters were determined. It was specified that the best particle size was d80=600 microns, 80kg/t of H2SO4 consumptions, 2 hours of leaching time at 40 centigrade temperature, MnO2 type of oxidant with 5kg/t consumptions, and at equal ratio of liquid to solid (L/S). The recovery of uranium was also cross-checked, running a test using a sample with more weight, under the optimized parameters. The obtained results from this test indicated of 81% of uranium recovery which was acceptable and an indication to the previous tests results.

Determination of slope angle is one of the most important parameters in open pit mine design. With low slope angles, stripping is considerably increased. On the other hand, selection of high slope angles may reduce safety and causes failure. Therefore, to prevent slope failure and high stripping, a compromise is necessary to select an optimum slope angle. There are several methods of analyzing the stability of open pit slopes such as limit equilibrium methods, empirical methods and numerical methods. In this paper, FLAC software has been applied to determine the overall slope angles in the different parts of Sungun copper mine. For analyzing the slope, five vertical sections with a proper coverage of all parts of the mine, were considered. For the aforesaid sections on the static loading, stability analysis was performed for different slope angles and then with the help of regression analysis a relationship was developed between safety factor and angle of slope for each of the sections separately. In this research work, on the basis of geo-mechanical characteristics of rock mass, a factor of safety of 1.2 was selected. On the basis of obtained results, mine slope in the south and south-west was detected to be critical. Based on this analysis, slope angle of the mine, in the south and south-west parts and for the north and north-east part, was considered to be 25 and 37 degrees respectively. Sensitivity analysis was fulfilled for each section to study the role of cohesive strength and internal friction angle. It was considered that section 4800 (west) and section 4800 (east) respectively have the highest and lowest sensitivity to variations of cohesion. Also it was seen that section 4800(east) and section NE-SW respectively have the highest and lowest sensitivity to variations of internal friction angle.

Particle size control of feed entering to mineral processing equipment which is essential in optimization of circuit performance is normally performed by hydrocyclones. Increase in hydrocyclone dimension increases cut size. Therefore its application in industrial scale follows difficulties. In Contrast, cut size of Reflux classifier obtained with combination of inclined separator and fluidized bed classifier is independent from dimension. In this work, classification performance of reflux classifier for possibility of cut size about 45 microns was investigated. Capacity and cut size of Reflux classifier was 9.3 to 15 t.m-2.h-1 and 74 to 132 microns, respectively. Also linear correlation in the form of Y=aX between water flow rate in overflow and cut size was observed that can be used in design and scale up stage. On this basis the capacity of reflux classifier for about 45microns was estimated equal to 5.12 t.m-2.h-1

Particle size control of feed entering to mineral processing equipment which is essential in optimization of circuit performance is normally performed by hydrocyclones. Increase in hydrocyclone dimension increases cut size. Therefore its application in industrial scale follows difficulties. In Contrast, cut size of Reflux classifier obtained with combination of inclined separator and fluidized bed classifier is independent from dimension. In this work, classification performance of reflux classifier for possibility of cut size about 45 microns was investigated. Capacity and cut size of Reflux classifier was 9.3 to 15 t.m-2.h-1 and 74 to 132 microns, respectively. Also linear correlation in the form of Y=aX between water flow rate in overflow and cut size was observed that can be used in design and scale up stage. On this basis the capacity of reflux classifier for about 45microns was estimated equal to 5.12 t.m-2.h-