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By S. H. Shahcheraghi

The four operational parameters including collector dosage, frother dosage, conditioning time and pH, are the most important parameters effective on the flotation kinetic. The present study has been done at the Miduk Copper Complex in the province of Kerman. The effect of operational parameters on the flotation kinetic of copper minerals were studied and analyzed, so the optimum conditions for flotation kinetic of copper sulfide minerals were obtained. Under the obtained optimum operational conditions, the recovery of copper sulfide flotation at the 95% confidence level was estimated to be between 92.76% and 95.48% and the copper sulfide flotation kinetic constant was estimated to be between 1.40 and 1.45 min-1. Results showed that the consumption of the X231 collector (O-isopropyl-N-ethylthionocarbamate) and the A65 frother (Polypropylene glycol) could decrease up to 35% and 50% respectively while the copper sulfide recovery increases about 1 up to 2% at the laboratory scale. Keywords: flotation kinetics, sulfide copper, optimization, the Miduk Copper Complex, response surface method

Sep 1, 2012

By V. Hema

Granular materials are widely used in process industries, such as chemical, pharmaceutical, cement, food, detergents, and fertilizers. Mixing, blending, calcining, reduction, heating, and granulation of these materials are frequently carried out in rotating cylinders. In all of these processes, the mixing and segregation of these granular materials is important as this controls the secondary phenomena in the rotating kiln such as heat transfer to the material. A significant amount of work is available in the literature but to date these efforts have not been able to capture the important parameters affecting the mixing and segregation in rotating kilns. In addition, the range of parameter values studied so far is rather limited. Simulations of granular materials are based on either discrete elements or continuum models. The discrete element methods (DEM) combine semi-empirical models for the inter particle interactions with the equations of motion from classical mechanics to simulate the explicit paths of all granules in a rotary kiln, thus yielding realistic predictions of the mixing process. This approach is very demanding computationally, which strongly limits the number of granules and the number of revolutions in a simulation. Continuum models dispense with the discrete particles and can therefore be scaled up more easily. But the constitutive relations that serve as the foundation for continuum modeling are difficult to come by, and often only applicable to specific systems and conditions. Here we have chosen DEM simulation for investigating the mixing and segregation behavior of granular materials in a rotating cylinder. This work is directed towards demonstrating the capability of the prediction of the mixing and segregation behavior of granular materials in a horizontal rotating cylinder through discrete element simulation. Further the effect of particle size and rotational velocity on the mixing and segregation behavior is investigated. The simulation results are quantified in terms of mixing index, mixing rate, segregation index and percolation index. Keywords: DEM simulation, granular mixing

Sep 1, 2012

By Juan B. Yianatos

"After almost 100 years, since the first commercial application began in Australia, flotation has shown an extraordinary growth and nearly 2 billion tons of ore per year are presently treated by flotation processes. During this time flotation has promoted a wide scope of research activities ranging from fundamental chemistry and hydrodynamic studies to studies of industrial operations. In general, fundamental studies have been mainly related to ideal situations. In recent years, however, large efforts have been focusing on achieving a better insight into the actual sub-processes provided by the development of new and more sophisticated instrumentation. Since the massive incorporation of flotation columns, around 15 years ago, a renewed interest in flotation fundamental studies, process modelling and new cell designs have been observed worldwide. The key role of the froth has been recognized as an independent and sometimes rate limiting process step. Thus, separation of pulp and froth process stages seems the most appropriate in terms of process modelling, diagnostic, design and scale-up purposes.In relation to flotation equipment development, until the middle of the 1970?s, only the sub-aeration mechanical cells were dominant. Since the 1980?s, the use of pneumatic cells and forced air mechanical cells has emerged strongly. Also, in the last decade, flotation equipment has shown a dramatic increase in size, reaching values of 200m3 in unitary mechanical cells and more than 300m3 in columns. The general feeling, however, is that, despite the great advance observed in terms of process knowledge, the mechanisms and principles of industrial flotation cells design and scale-up are still not fully understood.Advances in process instrumentation and control now in use allow for more efficient operations, both in metallurgical performance and savings in operating costs.INTRODUCTIONFlotation is a widely used process within the minerals processing industry, as well as being used for water treatment and de-inking of recycled paper. Froth flotation started in Australia at the beginning of the 20th century and since then flotation technology has made significant advances. Flotation was firstly applied to sulfide ores. The largest tonnages treated by flotation are copper and copper/molybdenum ores, handling about 50% of the total ore processed. Also significant are phosphate, iron ore and coal treatments. At present, Chile is the foremost copper producer in the world with around 35% of the world?s production. Figure 1(a) shows the evolution of copper production in Chile over the last decade. The total amount of fine copper produced in year 2001 was 4.7 million tons, from which 3.2 million tons was processed by flotation while 1.5 million tons went through LIX-SX-EW processes, which also showed significant development during the same period (Anon, 2001). The total flotation treatment of copper ores in Chile is about 325 million tons per year (Anon, 2002), so the world treatment of copper ore by flotation can be estimated at about 1 billion tons per year. Consequently a total of nearly 2 billion tons of ore per year is presently processed worldwide by flotation (Fuerstenau, 2001). In order to handle the higher tonnage of low-grade ore, a worldwide trend towards the development and use of larger flotation machines began in the 1960?s. Figure 1(b) shows that the trend became extremely marked from the beginning of the 1990?s, which is consistent with the strong increase in copper production during the same period."

Jan 1, 2003

By Ye Junjian

The feed ore is the concentrate of low intensity magnetic separation of pyrite tailings, containing TFe47.47%, S19.41% and SiOpyrrhotite. The exploratory tests showed that using a process of flotation followed by magnetic separation could respectively obtain a sulphur concentrate of S 31.08% with a recovery of 82.89%, and an iron concentrate of TFe 59.97% and S 9.52%with a recovery of 30.93%. The reason of iron concentrates with high sulphur grade was that the sulphur grade of flotation tailings was 7.03%. So enhanced flotation for pyrrhotite was investigated in this research. Results show that when the natural pH of ore pulp varied from 5.5 to 6.0, a reagent combination of FS, LH, and BJ displayed the optimum flotation performance for pyrrhotite. After comparisons made on different flotation processing, the previous flotation flow of ?one roughing, one cleaning, one scavenging system and middling reprocessing?, was found, among others, to have the best flotation effect, as the grade and recovery of sulphur concentrate were 31.08% and 82.89%, respectively, and sulphur content of the flotation tailings was 7.03%. The above results indicated it was difficult to raise further the effect of flotation desulphurization. The authors therefore suggested that oxidizing roast should be adopted following the magnetic process for the purpose of further desulphurization. Besides, flue gas containing SO2 8.25%. And the valuable minerals are magnetite and 2 generated from roasting could be reused for sulphuric acid production. Keywords: pyrrhotite, enhanced flotation, desulphurization

Sep 1, 2012

By Kazutoshi Haga, Batnasan Altansukh, Shirchinnamjil Nyamdelger, Atsushi Shibayama, Narankhuu Ariunbolor, Gunchin Burmaa

In this study, the authors investigated the capability of an acidic thiourea solution and silicon-organic polymers (PSTM-3c, PSTM-3T) as ion-exchange resins to recover of gold from gold-bearing ore concentrates. Firstly, elemental gold present in flotation concentrates was dissolved by leaching with a solution of nitric acid and thiourea under the optimized conditions. The best result on gold thiourea leaching was obtained under a nitric acid concentration of 2 N, thiourea concentration of 2 %, and oxidant (Fe2(SO4)3) concentration of 3 %, solid:liquid ratio (S:L) of 1:20, leaching time of 6 hours at 20 °C with a gold recovery of 93.7 % for a gold flotation (unroasted) concentrate. For the roasted gold concentrate, the dissolution of gold was 94.8% under the optimized leaching condition as nitric acid concentration of 0.5 N, thiourea concentration of 2 %, and the oxidant concentration of 1 %, S:L ratio of 1:10, leaching time of 4 hours at 50 °C. Secondly, a series of sorption tests was carried out on a pregnant leach solution containing gold complex Au[S=C(NH2)2]2+ using silicon-organic polymers (PSTM-3c and PSTM-3T), respectively. The effects of solution pH, adsorption time and temperature in the sorption process are also studied. As the results, the PSTM-3c and PSTM-3T polymers were adsorbed about 94.4 % and 95.1 % gold from the pregnant leach solutions under the optimum sorption conditions, respectively. It was found that the both PSTM-3c and PSTM-3T polymers were effective for the recovery of gold from the pregnant leach solution of thiourea. Adsorption activity of the PSTM-3c and PSTM-3T polymers was confirmed by new peaks near 1700 cm-1 in the FT-IR spectrum of the gold-adsorbed polymers, respectively.

Jan 1, 2014

By A. R. Videla, P. R. Brito-Parada, I. Mackay

"Linking results from laboratory scale experiments to industrial flotation behaviour is challenging. Typically, such experiments involve batch tests in which the system does not operate at steady-state, making it difficult to infer the effects that operating conditions have on flotation performance. In order to overcome this limitation a 4-litre recirculating tank was previously developed at Imperial College London. This tank is capable of reaching, and operating at, steady-state by recycling overflowing concentrate back into the feed. As well as instruments to control operating conditions, it is fitted with a system of sensors that allow the surface of the froth to be dynamically monitored. From this information, it is possible to measure the air recovery—a proxy for froth stability. Thus, this bench-scale tank can be used to understand the effect of differing operating conditions on flotation performance at steady state. However, so far, this cell has only been used to investigate idealised systems with only one or two species.Reprocessing of tailings dams is not only environmentally desirable but also increasingly economically feasible due to the declining head grades of primary deposits. There is also the added benefit of no further milling being required prior to flotation. However, the effects of fine and ultrafine particles on froth stability are not yet fully understood. In this work, the bench-scale continuous tank has been used for the first time to determine the flotation response of a complex feed, consisting of samples from a copper tailings dam, to changes in operating conditions. It was shown that the froth stability in the system is comparable to that of previous work and industrial tests, with a peak in air recovery being found at a superficial gas velocity of 1.13 cm/s. There is scope to optimize the froth stability of tailings flotation for enhanced metallurgical performance."

Jan 1, 2018

By Brian Hart, Liuyin Xia, Staman Dimov

The recovery of rare earth elements (REE) is fast becoming of significant interest globally. Modern research and development programs (outside China) towards the optimization of REE mineral recovery by flotation have been lacking. Due to the mineralogical nature of many hosting deposits, the separation and recovery flotation flowsheets can be very complex. As part of a research project, a selected suite of hydroxamic acid collectors (Naphthoyl, Cyclohexyl, Benzoyl, Octyl, Terta-butyl benzoyl, Salicylic) were tested in order to examine their potential for recovery and selectivity. Micro flotation tests were conducted on a feed sample, recovery and grade of the products were used to evaluate their relative flotation efficiency and selectivity and these results (flotation with the hydroxamate collectors) were compared to a phosphoric acid/sulphonate collector mix(shorten as "mixed"). In the testing, the flotation response with the hydroxamate collectors was significantly better than the "mixed" collectors on freshly ground (no slimes removed) samples. Furthermore the tests revealed that for most of the hydroxamate reagents tested, their dosage requirements to achieve recoveries at the same levels was less than that for the "mixed" reagents. Product assays show that recovery of both La and Ce is significantly better for using the salicylic hydroxamate and that Nb, Y and Zr recovery are favored by using octyl hydroxamate. These results indicate mineral flotation selectivity could be achieved by using selective hydroxamtes. Spectral fingerprinting by TOF-SIMS surface analysis has allowed for the identification of reagent species. TOF-SIMS surface analyses of grains analysis confirmed that REE bearing grains reporting to the concentrates are doing so in response to collector attachment whereas grains reporting to the tails are doing so in response to a lack of collector. The TOF-SIMS surface data bas been used to examine the factors promoting flotation stream partitioning.

Jan 1, 2014

By A. I. Arol

Bentonite is an important industrial mineral with very wide application areas. Its unique colloidal, swelling, thickening and adsorption properties make it a useful agent in drilling, metal casting, and iron ore pelletizing, environmental, food, cosmetics, pharmaceuticals and many more industries. Because of its swelling property, bentonite suspensions can only be prepared at rather low solid coentrations, i.e. 8-10%. In order to process bentonite in slurries with high solid content, it was thought that a non-polar organic solvent, instead of water, can be used. Not only large amounts of bentonite can be dispersed in organic solvents but also the solvents may be regenerated. The bentonite obtained through such a process must either equal or better properties than those of untreated bentonite. In this study, the effect of organic solvents such as acetone, methyl-ethyl ketone and n-haxane on the main properties of bentonite, such as water adsorption and rheology, was investigated. It was found that bentonite can be dispersed in the mentioned organics in large quantities with no loss of quality. Keywords: bentonite, montmorillonite, water adsorption, industrial minerals

Sep 1, 2012

By Yuliy Rubinstein

"The paper presents a analysis of the history and the trends of development of flotation apparatus. The laws of their evolution are stated and the place and role of column flotation are indicated. It is demonstrate development and different design of column apparatus. The major parameters of column cell such as diameter and height are discussed. Options are proposed on optimization of hydrodynamic characteristics of columns with large-capacity cells. High efficiency of columns with cell height of 4-6 m is shown on examples of coal preparation. A new generation of multi sectional column cells has been developed. In the cells are zones with different aerohydrodynamic parameters: combined in the machine are co-and counter- counter flows of phases. The transition from single-chamber column to multi-sectional apparatus makes it possible to create favourable hydrodynamic and aeration regimes in each section of the column dependent on the pattern of material distribution by floatability. Efficiency of application different designs column apparatus uses shown on the example of enrichment of various non-ferrous metals ores and coal. The principles of mathematical simulation of the flotation process are developed. A scaling-up procedure for column cells was based on flotation macro- and micro- dynamics simulation.INTRODUCTIONColumn flotation is considered to be one of the most significant achievement in the field of mineral processing in the end of last century. We cannot but agree with this statement but would like to understand what underlies this success. History of the flotation column can not be considered in isolation from the development of flotation apparatus on the whole. It can be argued that the first attempt to switch from oil flotation to the use of bubbles during flotation was performed Bessel brothers in 1877 (Berlin patent 42 class 22, July 2) and in 1886 (Berlin patent 39,369 May 12). According to these patents, the crushed ore was mixed with oils , hydrocarbons and water. Then the pulp received in this way was heated up to boiling . Air bubbles and steam formed during boiling facilitate the flotation of ore particles coated with oil (first patent) or bubbles been generated by the reaction of lime with acid (second patent). The evolution in the design of the flotation apparatus incorporates the following key stages. Further development is connected with the Francis Elmore’s idea to use gas bubbles received at water electrolysis (UK, 13578; 1904). This method was not introduced then, but much later, in our time and on the essentially new technical basis it found a use for sewage treatment (electroflotation). Gas bubbling under vacuum patented also by Elmore (UK, 17816; 1904) obtained a practical use. It should be noted that the method did not lose its importance till now. The design of the camera has been surely optimized (Glembotskii etal, 1963). A year later A. Macquisten (UK, 26712) developed pressure (compression) flotation. Thus, the H.Sulman, H.Picard, D. Bell’s (US, 853120, May 29, 1905) basic patent and the adjoining T. Goover’s patent 1910 (US, 953746) formed the basis of the first and most important element of modern flotation: flotation with air bubbles sucked in from the environment. In 1914, J.Callow received a patent for on an apparatus where air was sparged through the porous false bottom of the cell ( US, 1104755). Woolen fabric folded four times was fixed on a perforated metal frame to be used for air sparging (Gaudin, 1932). The following year Durrel created the prototype of the injection (ejector) apparatus. The jet aerator made it possible to significantly reduce the size of the bubbles, in comparison with the filter cloth. An apparatus with slurry pre-aeration in an airlift prior to feeding into separation cell was developed Wagner in 1917 (US, 1235083). And finally, the first column apparatus with a counter-current of slurry and air was developed by M. Towne and S. Flynn in 1919(US, 1,295,817). ("

Jan 1, 2018

By Gus Van Weert, Samuel A. Bolorunduro, David B. Dreisingerm

"As deposits of high-grade base metal sulphides become depleted, attention must be focused on the treatment of complex sulphides, which contain significant fractions of precious metals such as gold and silver. Acid pressure oxidation is a promising process for these materials and the recovery of silver and gold will improve the economy of the process. Gold can be recovered from the oxidised residues, however, silver is incorporated into the jarosite specie and the cyanidation of the resulting residue yields very low recovery.Pressure oxidation of various complex sulphides was carried out at 110-150°C in sulphate media with additions of potassium iodide under conditions similar to industrial autoclaving. The resulting residues were subjected to cyanidation. High recovery of silver, up to 98%, was achieved because its incorporation into lead-hydronium jarosite during the pressure oxidation was minimised, while its deportment into the cyanide-soluble silver iodide was favoured. Silver recovery decreased slightly at high temperatures (140° and 150°C) because of the enhanced stability and kinetics of lead-hydronium jarosite, but this could be overcome by increasing acidity and iodide concentration of the autoclave slurry."

Jan 1, 2003

By Seungwoo Park, Gaurav Soni, Roe-Hoan Yoon, Hyunsun Do, Kaiwu Huang

In a flotation froth (and foam), air bubbles become larger due to coalescence, causing bubble size to increase, bubble surface area to decrease, and hence casing less hydrophobic particles to drop off to the pulp phase below. Thus, bubble coarsening provides an important mechanism by which product grades are increased. On the other hand, excessive bubble coarsening results in low recoveries. In the present work, a model describing the process of bubbles becoming coarser in a foam as they rise to the top by deriving a mathematical relation between the Plateau border area, which controls film drainage rate, and the lamella film thickness, which controls bubble-coalescence rate. The model has been derived by assuming that liquid drainage rate increases due to slip at the air/water interface, and that the critical rupture thickness is determined by the capillary waves created by thermal motion. The model developed in the present work can predict the bubble size ratio between the top and bottom of a foam as functions of aeration rate, foam height, and surface tension (frother dosage). The model predictions are in good agreement with the changes in bubble sizes measured using a high-speed camera.

Jan 1, 2014

By S. Nitta

The present study deals with a new approach in calculating the size of Tower Mills. The method is derived from the application of grinding kinetics theory on the analysis of by-gone operational data. It requires only information on the capacity of the mill to be designed, the product fineness and the Bond?s work index to give an accurate and simple prediction of Tower Mill characteristics. An example illustrates the different steps of calculation.

Jan 1, 2014

By Mario Gerards, Marco Steinberg, Jan Huben

"Wet high intensity magnetic separation or WHIMS is a widely used technical process for the recovery of magnetic susceptible iron ore particles, mostly for fine and ultrafine grain sizes. The JONES® WHIMS - Wet High Intensity Magnetic Separator, has been used for many years and in countries all around the world. This paper outlines the physical principles utilized for the separation inside the unit, as well as some of the recent changes and developments on the design. It will also give an outlook on the theoretical potential of different alternative yoke materials. The aim of this paper is to analyse the suitability of different yoke materials to improve the equipment. This will be done comparing the magnetic and mechanical parameters and analysing availability and price to find the best compromise regarding cost and benefit. As far as the different kinds of materials are concerned, a special material has been identified as suitable during the comparison exercise. After running the economical calculations, especially with respect to the reduction of the total power consumption of the equipment, a tremendous reduction of the total power consumption has been determined. In addition, to the theoretical exercises and due to the promising results of the same, the Pilot Unit P 40 of the JONES® WHIMS has been manufactured with the special material in order to get practical results as well. Finally, this paper outlines the theoretical and practical results focused on the power consumption. The results are showing that the total power consumption can be reduced tremendously. Hence, the way for a new generation of JONES® WHIMS - environmentally friendly - has been paved."

Jan 1, 2014

By S. Kelebek, M. Davidson

"Flotation tests were conducted on a mixed copper ore sample containing bornite and malachite with trace quantity of other secondary copper minerals. The bornite component was very floatable, in sharp contrast to poor flotation characteristics of other copper minerals. A Box-Behnken experimental design methodology was used to study effects of three main reagents, namely potassium amyl xanthate (PAX), hydroxamate (Cytec 6494) and diethylenetriamine (DETA). Pine oil, as a frother, was used at a fixed concentration. Three main models constructed using a statistical software included malachite recovery, overall copper recovery, and copper grade. Bornite recovery was not modelled as its recovery was consistently over 99 % in the presence of hydroxamate and PAX. In each model, the hydroxamate dosage was the dominant parameter (at 95% significance level) determining the recovery of main components including that of gangue, which manifested itself by lowering the copper grade of the concentrate. In comparison, PAX was effective only at 90% significance level. DETA did not affect the overall recovery of copper or malachite significantly, but appeared to cause a significant decline in the concentrate grade, especially when used simultaneously with hydroxamate. Various quadratic models developed for the flotation system investigated are presented."

Jan 1, 2014

By Aysan Molaei, Kristian Waters

Solvent extraction is the one of the most common techniques for recovering metal ions from aqueous systems. However, solvent extraction is generally limited to relatively high concentrations and requires a high organic/aqueous ratio. Predispersed solvent extraction (PDSE) is a modified solvent extraction technique in which organic phase pre-comminute into colloidal liquid aphrons (CLAs). In this study, the extraction of copper by the PDSE technique was investigated. The main focus of this study was on the characterization and application of CLAs under different operational conditions, and to investigate the effects of different parameters on the extraction of copper from dilute streams. The effect of phase volume ratio (PVR), initial extractant concentration and initial copper concentration was studied and optimum conditions for copper removal using CLAs generated by LIX 984N as extractant, oil soluble and water soluble surfactants were proposed. Experimental observations indicated that PVR and initial LIX 984N concentrations had a significant effect on copper extraction.

Jan 1, 2014

By J. Drzymala

Ores and raw materials are subjected to mineral processing operations to increase the content of their useful components. Upgrading of these materials can proceed with different selectivity and therefore, there is a need to know and monitor the separation results of the process. The separation results can be evaluated using tables and graphs called upgrading curves. The course of lines in the upgrading curves is usually complex and depends on the graph type and process parameters. The Halbich grade vs. recovery plot is frequently used because is practical and it indicates several characteristic features of separation results. Separations by means of flotation of several different shale, dolomite and sandstone copper ores were performed along with determination of their mineral composition, copper content, liberation degree, and the maximum theoretical copper content in the first concentrate. These data, plotted as the Halbich upgrading curves, allowed to find other characteristic points such as practical maximum copper content in the first concentrate, maximum curvature coexisting with the liberation degree, maximum recovery of ore valuable components, and the slope the recovery-grade line at high recoveries as a measure of liberation. Correlations between theoretical and practical maximum copper contents in the first concentrate as well liberation degree and maximum curvature were also presented. They show that the ore type significantly influences the shape of the Halbich curve and its characteristic points.

Sep 1, 2012

The ball level and pulp load play a key role in the operation of industrial scale ball mills. These two operating variables have a significant influence on the performance of the ball mill and any attempts to optimize these devices require manipulating either one or both of these variables. There are several models that can be employed to perform simulations to optimize the performance of industrial ball mills. However, most of these models require ball load and pulp load measurements as inputs to calibrate the model. The changes suggested by the simulator also provide operating regimes that involve moving either the ball level or pulp load and sometimes both of these variables. A ball mill model coded in JKSimMet was used in conjunction with the Sensomag to optimize the secondary ball mill at Waterval concentrator in South Africa. The results show that the perfect mixing ball mill model can be used in conjunction with the Sensomag to optimize the performance of the secondary ball mill.

Sep 1, 2012

By David I. Verrelli, Peter T. L. Koh

"Recent experimental measurements of induction time made by direct observation with the ‘Milli-Timer’ indicated that angular particles were able to attach much more rapidly than spherical particles. There was around a tenfold difference in the respective induction periods for particle-bubble attachment. For industrial application, a more holistic comparison is needed, with the induction period for attachment being just one input. Over the years, CSIRO has developed a CFD-flotation model that incorporates both rigorous hydrodynamics, to simulate real industrial cell geometries, and a detailed model of the embedded flotation process, in which the induction period is an important parameter. We conducted transient modelling of batch flotation. First, spherical particles were modelled, as a ‘baseline’, for different particle sizes and levels of hydrophobicity. In the second set of results, the induction period was decreased by a factor of up to ten, simulating flotation of angular particles. Flotation recovery was found to depend upon induction period in a complex manner. For highly hydrophobic or fine particles, the induction period for spheres was already so low that recovery was limited by other factors (e.g. bubble-particle collision frequency). Further decreases in induction period, as for angular particles, did not have a significant effect on recovery in these cases. By contrast, when weakly hydrophobic or coarse particles were modelled, the recovery was predicted to be greatly enhanced for angular particles, in comparison to spheres. For these particles the induction period was limiting recovery, so that the flotation rate constant could be improved directly by reducing the induction period. This is consistent with batch flotation experiments using Ballotini reported earlier. Therefore, when dealing with weakly hydrophobic particles or relatively large particles that are to be floated, an enhancement can be expected for more angular particle shapes. In such cases, judicious specification of the grinding circuit may improve the overall efficiency."

Jan 1, 2014

By P. S. Mukherjee

Mineral ilmenite is a major resource for titanium, whose major application is for production of Titanium dioxide (TiO2) for pigment application. The production of pigment grade TiO2 from ilmenite was earlier carried out by acid leaching, which has now been banned due to environmental regulations. Further acid leaching leads to loss of iron metal values as sulphate or chloride which are also treated as effluent. In thermal plasma processing the metal values are recovered as high value pig iron and Titanium dioxide is recovered as Titania rich slag containing 80 to 85 percent TiO2. The Titania rich slag has now been considered as a better input material than synthetic rutile for production of pigment grade Titanium dioxide. On the other hand, high value pig iron goes for automobile industry for specific application. An Inflight-flight Thermal Plasma Processing plant, used for the production of Titania Rich slag and high value Pig iron from ilmenite, with 20kg capacity was designed and fabricated. The reactor has the provision to utilize the flue gas generated for preheating the input of raw materials. Various aspects of designing the furnace operation include viz. Feeding the raw material at a fixed rate, designing the crucible used for melting ilmenite, proper cooling arrangements, an innovative method for tapping the melt, recovery of heat from the gases, various safety arrangements which are some of the important milestone of the present work. The various operations have been carried out through a controller panel. Experiments were carried out to optimize various processing parameters using statistical modeling. Large scale experiments have been carried out at 10 to15 kg scale. The material balance has been calculate, and it has been observed, that about 95 percent recovery could be obtained for both Iron and Titanium oxide from ilmenite. The detailed characterization on Titania rich slag and iron has been carried out. It has also been shown that using the above slag, it is possible to prepare nanosized Titanium dioxide powder containing about 98 percent Titanium dioxide by optimizing leaching conditions. Keywords: titania rich slag, ilmenite, thermal plasma

Sep 1, 2012

By Carin Laubscher, Francis W. Petersen, Jaap P. Smit

Waste streams, such as acid mine drainage, are often characterised by low pH values and high concentrations of heavy metals, dissolved solids, calcium and sulphates. Although lime remediation effectively removes most of the heavy metals as hydroxides, it is less effective at lowering levels of sulphates. Various methods of removing sulphates from effluents exist, such as precipitation with lime, precipitation with barium salts, co-precipitation with calcium carbonate, reverse osmosis, and ion exchange. Mintek developed a chemical precipitation (SAVMIN) process to treat acid mine drainage, which entails the addition of lime to precipitate the metal hydroxides, and the subsequent formation (precipitation) of calcium sulphoaluminate or ettringite. The key to the viability of the new technology lies in the correct use, regeneration and recycling of Al(OH)3 used to precipitate the ettringite. The water produced by this process is suitable for disposal to watercourses or for agricultural, domestic or industrial consumption. No brines are produced as the salts are converted to solid hydroxides, gypsum and calcium carbonate. The technology has been tested on several different waters in pilot plant campaigns. Results obtained indicate that potable water can be produced (containing less than 200 mg/L sulphate and no heavy metals) as long as the monavalent ions (Na+, Cl-, etc.) are within limits.

Jan 1, 2003