Beneficiation
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Beneficiation is a variety of process whereby extracted ore from mining is reduced to particles that can be separated into mineral and waste, the former suitable for further processing or direct use.
Based on this metaphor, the term has come to be used within a context of economic development and CSR (corporate social responsibility) - to describe the proportion of the value derived from asset exploitation which stays 'in country' and benefits local communities.
For example, in the diamond industry, the beneficiation imperative argues that cutting and polishing processes within the diamond value chain should be conducted in-country to maximise the local economic contribution.
Beneficiation studies using various techniques such as hydrocyclone, spiral, magnetic separation, flotation etc. were carried out to develop a suitable process flowsheet as a step towards the up-gradation of Iron values and to reduce the gangue content. The required separation technique was selected based on particle size and the properties for effective separation. Initially, the hematite ore fines were ground to required size and then subjected to separation. The sample was ground to below 1.0 mm size for hematite ore fines and less than 100 microns for BHQ ore. However, the tailing samples from Goa ore have been treated without further grinding.
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Hydrocyclone was used as a step towards the upgradation of Iron values as well as for de-sliming of slime particles present in the sample. Since the ground samples contained large amount of slime materials comprising of particles down to sub micron size, de-sliming was also thought of prior to flotation. The effect of some of the variables namely apex diameter, vortex finder diameter, operating pressure, solids concentration etc. were optimized. The throughput of hydrocyclone during the experiments was 240 to 780 kg/hr solids and the solid concentrations of ~10-20 % by weight were maintained during the course of the experiments. The underflow and overflow materials were collected at a steady state for a fixed time, dried, weighed and analyzed for the desired Iron and other constituents. The overflow & underflow samples collected at optimum operating conditions were used for further studies.
The spiral concentrator of 100 mm dia. was used to enrich the Iron content of the classified sample (hydrocyclone underflow). The spiral is an energy saving gravity equipment where large quantities of sample can be fed for preconcentrations. In the spiral study, the Iron ore sample was fed to the centrifugal pump at the required solids consistency and the slurry was kept re-circulating for a predetermined time. The entire concentrate and tailings were collected after attaining the steady state. The concentrates in some cases were cleaned to improve the grade of products. All the products thus obtained were dried, weighed and analyzed.
The wet high intensity magnetic separator (WHIMS) and high gradient magnetic separator (HGMS) were used at different magnetic field intensities to recover the fine Iron values from the hydrocyclone over flow or spiral tailings. Both the separators have provision for different magnetic groves of width and matrix with variable currents to provide different magnetic intensities. A desired concentration of solids was passed through the magnetic separator. In some cases the magnetic products were cleaned in second stage to enhance the quality of the product from first stage separation.
Batch flotation studies were carried out to select either direct or reverse flotation technique to optimize reagent combination and to establish the number of stages of operations. Denver D-12 sub-aeration flotation machine was used for the batch flotation studies. Both cationic (dodecylamine) and anionic (oleic acid) reagents were used as collectors while MIBC was used as the frother. The flotation conditions were optimized to get good grade concentrate with high recoveries. The column flotation studies were carried out by using 100 mm diameter glass column designed and fabricated at our laboratory. The column was operated at nominal capacity of 20 kg of Iron ore fines per hour with the help of a peristaltic pump. Both the concentrate and tailings were collected separately after attaining the steady state and analyzed for Iron content.
