نشریه مهندسی منابع معدنی
سال ششم شماره 2 (تابستان 1400)

In this research, the optimum block size determination method and its influence on reserve estimation were investigated. For this purpose, the Kushk lead and zinc deposit data were used as case study. The database was built using borehole data and the composite samples were prepared with a 2m length. The data was transformed to Gaussian distribution by normal score transformation method. Variography was used for identification of variability and continuity of the ore, and the best variogram models and anisotropy ellipsoids were fitted. Due to ore complexity and density of boreholes in open pit and undergrounds, indicator kriging method was used for orebody modeling and ore-waste boundary determination. Considering different block size, the lead and zinc grade variability was modeled by sequential Gaussian simulation method. In each block size simulation, 20 realizations were determined and the variances between realizations were calculated. The lower variance is accordance with more similarity of realizations which was selected as a criterion of optimum block size determination. With this method, the optimum block size of Kushk deposit was determined as 10x10x7.5 m. The optimum block size is relatively accordance with the anisotropy ratio at the deposit, therefore it was chosen as suitable block size for reserve estimation of the deposit. By this optimum block size, and considering a 3% cut off grade for sum of lead and zinc, the reserve of the deposit was calculated about 39.12 million tons.

Geostatistical modeling, in recent years, has been widely and increasingly used in analyzing underground structures. Using the combination of uncertainty reduction techniques and modeling processes could increase the identification accuracy of underground structure models. In this study, Indicator Kriging (IK) method is employed to model four geological units comprising leached, oxidized, supergene and hypogene zones. The aforementioned units are all located within Miduk Copper Deposit. To evaluate the uncertainty index based on the modelled geological structure, Bernoulli variance is employed. In order to reduce the uncertainty amount of the executed geological model, post-processing procedure is performed using resampling of the interpolated model. This procedure is reiterated as many times as possible until a geological model with an acceptable uncertainty amount is acquired. At the final step, blast holes data is used in order for the validation of the results. The yielded results indicate that the amount of uncertainty dropped from 5.87% to 2.98% after implementing the post-processing procedure.

This research used prestack seismic data in Penobscot to detect gas-bearing layers using AVO analysis. AVO technique is not easy based on Zoeppritz equations then this work applied Shuey approximation to calculate gradient (G) and intercept (Rp) parameters using least square and Tikhonov solutions. Model covariance matrix was calculated for least square and Tikhonov technique to obtain the variance of estimation of Rp and G. The variance of estimation of least square method is 0.24 and 15.08 for RP and G, respectively. Also, it is equal to 0.08 and 0.14 for Rp and G in Tikhonov solution. Therefore, the results of Tikhonov are more reliable than least square solution. Multiplication of intercept and gradient showed the strong and positive values in gas layers. The reflection coefficient of shear wave identified gas-bearing layers by a positive value. The difference of P-wave and S-wave profile appeared relatively high negative values in time range of 2000 to 2020 ms. L30 well which was drilled in cross line 1153 showed that there is gas accumulation in time range of 2000 to 2036 ms. Therefore, AVO attributes could identify gas-bearing layers.

Production planning defines the drawpoint extraction percentage in order to a deterministic destination (processing factory) according to scheduling objectives. One of the main problems in such planning is related to the lack of integration designing factors. So, there is a need to develop a model for mine scheduling using all factors influencing the strategic plan. In the current study, the Mixed Integer Linear Programming (MILP) has been developed according to metallurgical constraints. The maximum and minimum cut of grade as well as relative grade constraints are used to produce a real production from drawpoints according to the dilution control. The CPLEX software is used as a MILP solving framework, and also MATLAB to develop mathematical models. The application of the models based on metallurgical constraints was validated using 85 drawpoints over 12 periods. The results showed that in usual condition, the reduction of NPV was only 9% with the proportional non-distribution of average grade 24% of the maximum grade in the drawpoints, while by applying the metallurgical constraint this was reduced to 4%. Finally applying the metallurgical constraints with other operational constraints presented the real production planning.

In the present research, the situation of chromite in Iran has been investigated in terms of production, import and export during 10 years period (1387-1396 in Persian calendar and 2008-2017) as well as the position of Iran has been determined in the world. Over these years, Iran ranked 10th in the world by producing between 1 to 1.5 percent of the world’s chromite production. Investigating the import and export of chromite ore and concentrates in Iran through 1388 to 1396 also reveals that while the export varies between 20 and 160 million dollars, the top of imports can’t even reach to 850000 dollars. Neighboring countries such as Oman, Turkey and Turkmenistan, Asian countries containing China, India and Japan and European countries like Spain make up the most important export target markets of Iran’s chromite, which China with 99.7 percent is the largest importer of Iran’s chromite. Iran ranked 6th in global exports of chromite but the presence of Iran’s rival economies in Asia and the Middle East such as Turkey, Kazakhstan and Pakistan in the ranking above Iran, predicates serious rivals in the region. During 2008 to 2017 Iran’s relative quota of the chromite global exports is between 1 and 6 percent. The results of the research show that the state of the country is promising in all three sectors of the production, import and export of chromite ore and concentrates. It means that by increasing production and appropriate planning on target markets, exports will also be increased in the future.

In this paper, the influences of joint angle and joint spacing on the rock fragmentation have been investigated using Particle Flow Code in two dimensions (PFC2D). Firstly calibration of PFC has been done using proper micro parameters. For this purpose, both of the Uniaxial test and Brazilian test have been done on the NX samples. These tests were simulated by numerical method and then the proper micro parameters have been chosen by try and error. After calibration, 21 models with dimension of 11cm ×10 cm consisting one joint have been prepared. The joint angels were 0°, 15°, 30°, 45°, 60°, 75°, and 90°. The joint distances from cutter were 1cm, 2.5 cm and 4cm. Shear properties of joints have been determined using simulation of direct shear test on the modeled joints. One u shape cutter with diameter of 2 cm was in contact to the model surface. Axial force was applied to the model trough cutter.  The results show that both of the joint angle and joint spacing have important effect on the failure pattern and final failure load.

A sulfide copper ore was crushed to 100% passing 3.36mm followed by grinding the crushed product through bed breakage process in a piston- die cell or ball mill into to 100% passing 250μm. Revealed by the results of particle size analysis made on the ground products, the bed breakage method provides a finer product compared to the ball mill approach. The liberation analysis of the products in eight size-fractions showed that the chalcopyrite in the ball mill product was more liberated compared to the bed breakage product. The overall percentage of chalcopyrite liberation in the ball mill product was higher than the bed breakage product by 1.82%. The shape properties of particles in the breakage products were examined by analysis of scanning electron (SEM) images. Accordingly, it was found that the circularity and roundness of particles broken by the bed breakage method are higher than the particles broken by the ball mill method, while the ball-milled particles are more elongated. The results of micro-flotation tests indicated the efficiency rate of Cu recovery and separation in the ball mill product were respectively 11% and 15% higher than the bed breakage product. This better metallurgical performance can be attributed to the fact that the bed breakage product was finer, the chalcopyrite was more liberated in the ball milling product, and particles in the ball milling product had less circularity and roundness. Contrary to many previous studies, the results of this study indicated that the bed breakage method did not increase the mineral liberation and improved the performance of the flotation process.

The aim of this study was to synthesize the organic nanocomposite for drug delivery using prosopis cineraria, and to investigate the loading and releasing the drug. The release of the tungstophosphoric acid hydrate was conducted with immersing 0.65 g of nanocomposite containing the drug in 50 ml of phosphate buffer at 37 °C under magnetic stirring conditions. The synthesis of the nanocomposites using pure merck silver nitrate (MSN) and silver nitrate from anodic sludge (SSN) after purification was statistically compared for pharmacological, microbicide and dewatering purposes. Since there was no significant difference between the two nanocomposites, the nanocomposites synthesized using SSN were used in all experiments.

The fluorescent powder contributes to up to 3% weight of compact fluorescent lamps, a significant portion of which contains rare earth elements such as yttrium and europium. These lamps are not recycled after usage, while they can be a good source for these elements. In this study, investigation on the process of dissolution and precipitation of yttrium and europium by hydrochloric acid and oxalic acid was targeted in order to find the optimal operating conditions. By measuring the pH changes, factors such as temperature, time, acid concentration, and solid-to-liquid ratio were determined to achieve the best leaching conditions. In addition, in the precipitation stage, the rinsing effect of yttrium hydroxide gels on increasing the purity of the product was investigated. The best leaching conditions were obtained by hydrochloric acid at 75 0C for at least 30 minutes and a solid-to-liquid ratio of 15 g/l in 0.3 M acid solution. The maximum precipitation of yttrium and europium oxalate, was obtained at pH=7. Rinsing the hydroxide gel by distilled water increased the purity of the product by more than 97% for the total of yttrium and europium, while 97% of europium and 99% of yttrium were recovered in the product.