محمدرضا گرمسیری

Compressibility of suspension plays an essential role in the performance of modern dewatering equipment such as paste thickeners and filters. Since compressibility of mineral suspensions is affected by interparticle forces, investigating the forces may lead to find a practical solution to enhance the compressibility of suspensions. Utilizing the surfactants is an essential method to manipulate the interparticle forces and enhance the compressibility of suspension. In this work, THE EFFECT OF anionic surfactants known as Sodium dodecyl sulfate (SDS) and Sodium Lauryl Ether Sulfate (SLES) on the compressibility and filterability of tailings of iron ore processing and their mechanism of performance was investigated. In this order, Buchner funnel tests were conducted to evaluate the effect of surfactants on the compressibility and filterability of the suspension. Then, settling tests were performed to evaluate the possible interaction between the surfactants and flocculant. Finally, measurement of zeta potential, drop shape analysis, FTIR and TG-DTA tests were conducted to assess the mechanism of the surfactants performance. The results revealed that the moisture content of the filter cake reduced by three percent in the presence of surfactants. It was also found that the mechanism of surfactants performance is changing the zeta potential and making the hydrophobic solids surfaces. Eventually, an interaction observed between flocculant and surfactants which caused the settling rate increased by five times. These results are promising to enhance compressibility (in paste thickeners and filters) in the presence of these surfactants and achieving more recycled water from tailings of iron ore processing would be viable. Thus utilizing advanced tailings disposal methods such as stacking and achieving sustainable mining in the presence of SDS and SLES.

Nowadays, one of the intractable challenges facing the minerals industry is the processing of complex ores. Processing of high sulphur content ore type is a major challenge in iron ore beneficiation. Thus, modification of mineral processing circuits to process iron ore with high sulphur content is essential. In this research, employing a regrinding section in iron ore concentrator aiming to reduce the particle size and improve the quality of concentrate in Golegohar concentrator line no. 4 was investigated. In this order, two different configurations were studied including regrind mill after high intensity (rougher, cobber) and low intensity (recleaner) magnetic separators. To assess the results of the circuit configurations, iron and sulphur grade, yield and blaine of concentrate were considered. Furthermore, the effect of particle size fractions with the d80 of 38, 45, 63 and 80 μm in the configurations was evaluated to find optimum particle size. Results indicated that the desired particle size in the reduction of sulphur content is +63-80 μm. Furthermore, utilising regrind mill after cobber resulted in a higher iron grade, yield and blaine while lower sulphur grade was attained with the regrinding after recleaner.

Circular vertical Spillway with various inlet forms is very effective, when there is not enough space for the other spillway. Hydraulic flow in vertical circular spillway is divided into three groups: free, orifice and under pressure (submerged). In this research, hydraulic characteristics are investigated in vertical circular spillway by using numerical model. Hydraulic characteristics are investigated such as upper and lower nappe profiles, relation between discharge and upstream water levels, and discharge coefficient in numerical modeling and experimental conditions. The mesh with 10602 nodes, turbulent model k- standard and the standard wall function, provide the best results for modeling the flow in a vertical circular Spillway. There was a good agreement between numerical and experimental results in the upper and lower nappe profiles. In study of water level over crest and discharge, in low water levels, the results of numerical modeling are good agreement with experimental, but with increasing water level, the difference between the numerical and experimental discharge to be more. In the study of the flow coefficient, by decreasing in P/R ratio the difference between the numerical and experimental result increases.

A major fraction of Chromite mine production is fine particles (-200 μm) which cause a serious challenge during the processing using gravity separators. From the other hands, these values need to be recovered to enhance the profitability of process and reduce the environmental impacts. Slon high gradient magnetic separator could be utilized in the processing of paramagnetic materials. In this work, the possibility of recovery of Chromite fines using a laboratory scale Slon was investigated. In this order, the effect of variables such as magnetic field intensity, particle size, matrix size and pulsing frequency was studied using the design of experiments. Results indicated that concentrate grade was dropped with increasing the magnetic field intensity. Furthermore, with a rise in pulsing frequency and a reduction in the matrix size, the concentrate grade was increased. Moreover, it was found that the concentrate grade higher than 40 % and recovery of 65-90 percent was achieved using laboratory scale Slon. Thus, it could be concluded that processing of Chromite fines using Slon is viable.

In mineral industries, most of the processes are carried out in an aqueous environment. With the purpose of reducing costs and environmental impacts,the water content of tailing stream should be recovered. Thickening is the most widespread method of water recycling process in mineral industries. In this work, the effect of solids concentration, flocculant dosage and particle size on settling flux and compressibility of copper processing tailings were investigated. Samples were collected from tailings of Shahrebabak copper complex and laboratory tests were conducted. In laboratory scale, settling flux and final height of suspension were examined using batch settling tests. In addition, thickener underflow solids concentration was considered as an indicator of the effect of variables in full scale. Results indicated that not only settling flux but also compressibility of the suspension was improved by reducing suspension solids concentration. Furthermore, it was found that increasing flocculant dosage from 15 to 45 g/t led to an increase in settling flux about 7 times. Moreover, both settling flux and compressibility were reduced with fine particles. Industrial scale studies showed that, increasing -75 μm fraction in thickener feed from 47 to 59 % led to a decrease in underflow solids concentration from 63 to 55 %.

Shear yield stress as a rheological property of suspensions affects the efficiency of some of the mineral processing methods such as solids liquid separation, grinding, classification, and tailings disposal. In this work, effect of solids concentration, fines extent, pH and temperature on the shear yield stress of the final tailings suspension of concentration plant 1 at Sarcheshmeh Copper Complex was investigated and eventually their impact on solids liquid separation was analyzed. The shear yield stress was calculated using the slump test results and the analytical model presented by Pashias. Results indicated that, with the extent of fines the shear yield stress increased considerably. An increase in flocculant dosage up to 10 g/t resulted in a significant increase in the shear yield stress. While, with the flocculant dosages higher than 20 g/t, increasing the flocculant dosage led to a slight increase in the shear yield stress. An increase in shear yield stress leads to a decrease in compressibility of suspension and as a result the efficiency of solids liquid separation decreases. These achievements can be beneficial to the efficiency of thickening and filtering.