R. Venugopal

The recovery of fine iron minerals from quartz and corundum mixtures using selective magnetic coating

The recovery of hematite fines from quartz and corundum using selective magnetic coating was studied as a function of pH, particle size, magnetic colloidal concentration, magnetic field strength and ratio of hematite:quartz. Synthetic mixtures assaying around 45–72% Fe2O3 was upgraded to 90–92% with recovery level of 90–96%. The optimum separation was observed at pH ∼7.2, colloidal concentration of 0.25 ml/g of hematite and a magnetic intensity of around 0.78 T. Electrophoretic mobility carried out on hematite, colloidal magnetite and quartz system showed a definite differences in their iso-electric points. The selectivity of coating was obtained by controlling the surface properties of the particle, the Zeta-potential being altered by pH adjustment and addition of sodium oleate. The separation of hematite from corundum was achieved by using a dispersant such as sodium hexa metaphosphate. Microscopic, XRD and FTIR studies strongly suggested the coating of magnetite on hematite surfaces. Experiments were also conducted with hematite, corundum and quartz mixture to simulate the condition of Indian iron ore slimes. The results obtained are discussed in this paper.

Recovery of Iron Values from Iron Ore Slimes by Selective Magnetic Coating

Effective separation of iron values from iron ore slimes using a wet magnetic separator and selective magnetic coating is reported. The selectivity of coating for enhancing the magnetic response of iron particles was achieved by controlling the surface properties of the particles, i.e., electrokinetics potential, through pH adjustment and use of sodium hexa-metaphosphates as the dispersant. Experiments were conducted with synthetic mixtures of iron, alumina, and silica using oleate colloidal magnetite at different fields of magnetic intensity. After the iron values were separated from the synthetic mixtures, the technique was applied to iron ore slimes of Joda area of India. Iron concentrate containing ∼65.9% Fe, 1.0% SiO2, and 1.56% Al2O3 was obtained from a feed containing ∼59.0% Fe, 3.98% SiO2, and 6.5% Al2O3. The effects of pH, magnetic intensity, and addition of sodium oleate were recorded. The X-ray diffraction (XRD) studies brought out the significant enrichment of iron in the concentrate relative to the feed, and alumina–silica enhancement in the tailing products. The scanning electron microscopy (SEM) study highlighted the coagulation of hematite and magnetite in the presence of sodium oleate, thereby facilitating the effective separation.

Performance and modeling studies of an MGS for graphite rejection in a lead concentrate.

The investigation is aimed at evaluating the performance of a Multi-Gravity Separator (MGS) in terms of rejecting graphite from a lead rougher flotation concentrate. The effect of change in different process variables on concentrate lead and graphite grades, lead recovery and graphite rejection values is studied. The results indicate that among the variables considered in this study such as drum rotation, inclination, wash water, amplitude and shake frequency, feed percent solids and feed flow rate, the change in drum revolutions influences the metallurgical results most. A suitable mathematical model for predicting the metallurgical performance under different design and operating conditions has been developed. The model included a set of equations relating the variables and the lead grade in the concentrate, lead grade and lead recovery, lead recovery and graphite rejection, and finally, the lead recovery and the graphite grade in the concentrate.

Characterisation and removal of iron from fly ash of talcher area, Orissa, India

Abstract Morphology, mineralogy and physico-chemical parameters of fly ash from Talcher area were studied. Morphologically it consists of spherical particles of varying size. Major minerals are quartz, mullite, hematite and magnetite. Elemental analysis and fusion characteristics of the material indicate the presence of class C type pozzolan with excellent pozzolonic properties and low slagging with medium fouling nature. In an attempt to remove iron from fly ash by selective magnetic coating followed by magnetic separation, the effects of pH, magnetic intensity, colloidal magnetite concentration and addition of sodium oleate have been studied. It is possible to remove around 92% iron at an optimum pH of ∼ 7.1 and magnetic intensity of ∼11.8 K gauss.

Artificial Neural Network Modeling of Ball Mill Grinding Process

Grinding consumes around 2% of the energy produced in the world but existing methods of milling are very inefficient and use only 5% of the input energy for real size reduction rest is consumed by machine itself. Chrome ores are comminute, filtered, pelletized and sintered to use into submerged arc furnace for ferrochrome production. Variation in ore properties affects the particle size distribution during milling. Artificial neural network based model is developed to predict the particle size distribution of ball mill product using grinding data available for difference in grindability of Sukinda chromite ores. Input variables for model were ball size, ball load, ball-ore ratio, grinding time. Output was particle size distribution (+75 μm, -75 μm, +38 μm; -38 μm). Three different kinds of mathematical models have been compared to predict the particle size distribution. Finally a neural network based model was found most accurate. Dynamic artificial neural network model does not require any material constant and optimizes the mathematical correlation with better accuracy in a dynamic process. This methodology can be used to develop an online system to predict the ball mill performance to improve the performance of grinding circuit in mineral, metal and cement industry.

Ore pretreatment methods for grinding: journey and prospects

ABSTRACT Pretreatment of ores to improve energy efficacy of grinding has been explored for decades. However, many of these techniques are still at developmental stages and a review has been presented in this paper to discuss the research journey and problems associated with commercialization of these techniques. This review reveals that a variety of stress-generating techniques have been used to treat the composition and morphology of particles to improve the grinding process. Grinding additives are used commercially successful technology while microwave pretreatment also has been successfully piloted. Newly developed techniques such as ultrasonics and electric disintegration have shown potential for success but the cost economics of these processes is still not as attractive as desired. Incipient techniques based on bio-milling, shock waves, and nuclear hold promise for the future. It is also expected that the technological advances around information technology, instrumentation, and energy science will help to solve techno-economic challenges associated with commercialization of the known technologies. Demand for energy-efficient grinding pretreatment methods will grow in the future considering the depletion of high-grade resources and stringent environmental constraints related to reject disposal.

Assessment and Mechanism Investigation of Selective Flocculation Process for Ultrafine Chromite Particle

During beneficiation of low-grade chromite ore, huge amounts of ultrafine tailings are generated and contain substantial metal values which need to be recovered. Selective flocculation technique is one of the processes for beneficiation of ultrafine particles. Here an attempt was made to establish selective flocculation process by using two types of synthetic mixtures. In addition to this, selective flocculation was also attempted on natural tailings. It was found that it is possible to enrich the chromite value using the selective flocculation process. The selectivity of the wheat starch to the chromite mineral was also investigated using image analysis, FTIR analysis, and zeta potential analysis.