خردایش

The reprocessing tailings of iron ore processing plants is important from economic (as a secondary source of iron) and environmental points of view. The aim of the present study is to determine the appropriate method for recovery iron from the tailings of Balestan iron ore processing plant (located in the northwest of Iran). For this purpose, after taking samples from the tail piles of this plant, a representative sample was selected, and chemical, mineralogical, size distribution, and bond’s work index analyses were performed on it. The total iron grade in the tailings was measured to be about 10%, of which 8.5% was identified as magnetite mineral (with a degree of liberation less than 40%). The d80 value of the sample was 7 mm, and the bond index was measured as 11.84 (kWh/ton). To determine the appropriate method for iron recovery, pre-processing with magnetic drum, grinding, and Davis tube tests were performed. With the magnetic pre-processing of tailings with a particle size of 0-10 mm, under a field of 2000 G and in a dry method, about 80% of the load entering the drum with a total iron grade of 5% was transferred to the tailings. 20% of the input load with an iron grade of approximately 24% was recovered to the concentrate. In order to remove the gangue minerals and enrich the pre-processed concentrate, stepwise grinding and separation had the best results. Comminution was done in two stages to produce products with smaller dimensions of 250 and 45 microns, respectively. Magnetic separation was also done in three stages with 3000 G, and two stages of separation with 1000 G, which finally resulted in a concentrate with a total iron grade of more than 66% and iron recovery of 44.88%.

Crushing is the first stage of operations involving size reduction and separation of ores. Throughput، feed and product size، rock compressive strength، and abrasion index among main criteria of crusher selection. In this Paper، Selection of different primary crusher type based on above mention criteria using Elimination Choice Translating Reality (ELECTRE) is discussed. The crushers that are considered include Double toggle jaw، Single toggle jaw، High speed roll crusher، Low speed sizer، Impactor، Hammer mill and Feeder breaker crushers. Results have been offered the Double toggle Crusher as the suitable primary crusher.

Control and online optimization of a process could only be performed if the dynamic model of the system is available. In the case of grinding circuits, dynamic simulation provides substantial information on complex and sometimes non-linear interactions between the components of the system. In this paper, dynamic model of ball mill and cyclone are incorporated in MATLAB/SIMULINK platform and then the system is simulated in open and closed circuits. Such simulation showed that the selected platform is suitable for investigation of responses of the system to the changes in input variables such as flowrate or mean residence time. It was also observed that the transient state between two steady states could be well investigated by the ease of this platform.

In Aghdareh gold processing plant, grinding circuit product size has a significant effect on downstream gold leaching process. Therefore, the performance optimization of hydrocyclone package in order to decrease the size of overflow stream to less than 70 μm (present value) will considerably increase the gold recovery. In this research, optimization of Aghdareh’s hydrocyclone package performance was done by application of Plitt’s model and its calibration and simulation of classification process. Two plant sampling campaigns were carried out to collect samples from the streams around the hydrocyclone package. Screen analysis tests were performed to obtain particle size distributions (PSD). Then, measured PSD and flow rates of various streams were adjusted using NorBal data reconciliation software. Then, BMCS (BMCS-based Modular Comminution Simulator) was used to predict the PSD of overflow and underflow streams for the first sampling campaign and also calibrating Plitt’s model to operating Aghdareh hydrocyclone package. Then, BMCS simulation predictions based on the calibrated Plitt’s model were validated using the second sampling campaign. The simulations showed that by using vortex and spigot internal diameters equal to 75 and 70 mm, respectively and with 6 operating hydrocyclones, the P80 of the overflow product can be decreased to 68.5 μm. Also, simulations by using vortex and spigot internal diameters equal to 94 and 53, respectively with 6 operating hydrocyclones showed that the separation sharpness, m, can be increased from 1.18 to 2.81 which indicates a 2.38 times increase in classification accuracy.