Journal of Mining and Environement
Volume:3 Issue: 2, Summer 2012

This paper utilises the modified Folchi method to assess the environmental impact of coal washing plant, Alborz Sharghi, North-east Iran. In this study, the number of factors designed in the method was slightly modified by focusing on the environmental impact of coal washing operations. In addition, few other factors were designed and added to the previous factors. Then, twenty-one values of environmentally impacting factors from the study area and a case with standard amounts of effects were calculated. This method was conducted by forming an assessment matrix in which one dimension is the environmental components and the other one is impacting factors to estimate the environmental problems arising from the impacting factors of both cases. Comparison of the results of two cases shows that the amount of contamination produced by the plant, especially for components including air quality, agriculture and area landscape is significant.

This study aimed to explore concentration of a low grade sulfide-oxide lead-zinc sample containing 2.3% Pb, 1.91% Zn taken from Changarzeh mine, South Natanz, Iran. The effects of different parameters such as type and dosage of collector, milling retention time, dosage of sodium sulfur and its preparation time, application of sodium silicate, pH and solid content were investigated in relation to flotation efficiencies. Optimum experiment was carried out in cumulative flotation with 200g/t KAX as collector, 2000g/t Na2S, 500g/t sodium silicate, 30g/t MIBC and at pH=10. This test yielded 94% of lead recovery under optimum condition performance, and a concentrate with 70%Pb was produced through cleaning stages. Eighteen minutes was found to be the optimum time for lead flotation in laboratory scale. Application of gravity method for the production of a middle product was also considered. For shaking table the effect of table slope and water flowrate and for jig the effect of water flowrate and frequency were studied. Gravity separation by shaking table resulted in a concentrate with 46%Pb and 80% recovery, so shaking table could be proposed for production of pre-concentrate.

Successful application of a TBM in a project requires investigating both the ground conditions and the machine and backup system design features. Prediction of the machine performance is very important as it has a big effect on the duration of the project and the costs. In this respect, both penetration rate and advance rate must be estimated. Utilization factor, which depends on the type of operation, management, maintenance, geological conditions, mucking delays and other downtimes, correlates the advance rate and penetration rate. Adverse rock mass conditions such as mixed face condition, water problem and instability of rock have a great role in TBM downtimes and reduce the machine utilization considerably. Based on detailed engineering geological reports and maps and daily site reports taken from Karaj-Tehran Water Conveyance Tunnel (Lots 1 and 2), this paper evaluates, main rock mass properties utilized for the estimation of TBM performance and discusses their effect on the machine utilization.. More specifically it uses the developed database also contains daily boring time, different rock mass related downtimes, daily advance and length of bored tunnel in each engineering geological units. It is concluded that the percentage of the rock mass related downtimes can be estimated via RMR within reliable coefficient of determination.

Using microflotation method, this study explored the collectorless flotation of Chalcocite and its dependence on the redox potential of pulp. Electrochemical studies were performed by cyclic voltammetry in specific potential ranges and at different pH values. The results show that significant floatability of Chalcocite occurs in the specific reducing conditions. By increasing potentials, on the other hand, the floatability of Chalcocite is reduced. The effect of pH was also examined: At pH=4, the maximum recovery of 73%, was obtained at E= -222 mV (Eh= -17); and at pH=9, the maximum recovery of 71% was obtained at E= -501 mV (Eh= -296). On the basis of the results obtained, the possible mechanisms of collectorless flotation of Chalcocite in different conditions were discussed.

The results of batch settling tests (BST) are used to investigate settling behavior of solids suspension, which contribute to sizing thickeners. Conventional methods in analyzing BST on the basis of visual and graphical procedures lead to sub-optimally sized and selected thickeners. A computational approach based on quantitative analysis of BST can be beneficial. About 300 settling experiments were performed by varying conditions, including solids concentration, type and dosage of chemical aids. Solid samples were collected from iron, copper, coal, lead and zinc tailings and feed streams. Settling curves based on experimental data considering extreme limits were generated and analyzed. Therefore, a mathematical model, h(t), is introduced to define batch settling curves. Furthermore, it is shown that, on settling velocity curves a maximum value is likely to occur (except in extreme conditions such as very high or very low solids concentration suspensions or extremely high dosage of flocculant). In addition, to compare batch settling curves quantitatively, an index, Ii, based on parameters which can be obtained from the model h(t), is developed. The proposed model and index can simply be utilized in a computerized approach of settling curves analysis.

The rapid growth in natural gas consumption has increased the need for gas storage, in particular in the form of injection into depleted reservoirs. Also, CO2 sequestration into the depleted reservoirs has attracted a large attention recently. However, it is important to ensure that the injection pressure is maintained below a certain limit to avoid unsealing the cap rock or reactivation of any existing fracture planes within or above the reservoir rocks. In particular, it can be thought that gas injection into formations with non-horizontal structures, such as anticlines, is more problematic than horizontal formations due to the development of shear zones in such geometries. This could potentially result in long term wellbore problems such as casing collapse or shearing along a fault or fracture plane intersecting the wellbore. In this study we compare the stress profile changes before and after gas injection into three structures: a horizontal and two anticline formations with different slopes at their flanks. For this purposes a 3D numerical simulator was used. The program was developed using finite element method (FEM) and the code was written in Fortran.The stress magnitudes along curved profiles were compared for three structures at a similar depth. A limited extension of a porous zone was assumed in this study. The results indicate how as structure becomes more curvy in its geometry the likelihood of shear displacement increases.

Altogether 20 groundwater samples were collected around the Lakan Pb and Zn mine in Iran. Samples were analyzed for 8 constituents including Fe, Pb, Hg, Mn, Zn, CN, SO4 and Cl using standard method. The results show that the average concentrations of constituents were 0.01, 0.60, 0.10, 0.01, 0.40, 35, 0.01 and 5.95 mg/kg for Fe, Mn, Pb, Zn, Hg, SO4, CN and Cl, respectively. The computed contamination index ranged between 2.38 and 443. It was concluded that contamination index shows a medium to high contaminated situation for Pb and Hg in groundwater around the tailings dam. Based on a multivariate analysis, four main sources of these hydrochemical data were identified. (1) Zn, Mn, TDS and SO4 have both natural and anthropogenic sources; (2) Hg constituent represents a natural source and Pb shows a anthropogenic source due to Lakan mine; (3) CN and Fe have anthropogenic source and mainly originated from the plant processing; (4) Cl represents a natural source.