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By Paula Olea, Gonzalo Montes-Atenas

Froth flotation operation is a large tonnage process aiming at selectively separate economically valuable minerals from gangue material. The wellbeing of an industrial froth flotation operation has been historically assessed and understood in terms of many variables known to somehow affect the process performance. Among these variables, air dispersion have been pointed out as key to secure the correct transport of hydrophobic particles to the froth phase and, then, to the concentrate. One of the classic parameters assessed when evaluating the air dispersion in flotation tanks is the superficial gas velocity. Many reports have focused on studying the superficial air velocity profiles across the pulp phase and theories have been based on the fact that the measurements should be performed in the so called "quiescent zone", which is a volumetric region inside a flotation cell of difficult determination. The hypothesis behind this research work is that the reporting of particles to the concentrate would provide a better correlation with the effective air flowrate pattern created in the froth phase. The aim of this study, as a first step towards developing a flotation model fully froth phase-based, is to estimate the effective surface area used in a flotation cell derived from results obtained with a specific setup at laboratory scale. The methodology considers running a thin lateral flotation cell cut at different superficial air velocities, with and without particles. It was found a non-linear correlation between the superficial air flow rate and the characteristic distance between the vertical wall next to the cell lip and the cut point where the foam or froth flowrate almost stops contributing marginally to the overall amount of solid particles transferred to the concentrate. The presence of hydrophobic particles reduced the mobility of the froth phase reducing the characteristic distance.

Jan 1, 2014

By D. J. Zhao

The reduction of ilmenite pellets was investigated at 950°C and 1000°C under a CO-N2 gas mixture with 10 L/min gas flow rate. All the reducing reactions were conducted in a furnace with a thermogravimetric analysis system. The reduction rate is higher at 1000°C than that at 950°C. At the early stage of the reactions, with the CO concentration increasing in the gas mixture, the reduction rate increased at 1000°C. In addition, at the early stage of the reactions, a rapid temperature increment and a rapid conversion of oxygen were observed on the curves of temperature versus time and conversion of oxygen versus time under different experimental conditions. The solid reaction products obtained in these experiments were analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometers (EDS). Metallic Fe with small amount of Ti dissolved in it and oxides of Ti were found in the solid reaction products, but the formation of any nitride phases was not found under the prevailing conditions.

Jan 1, 2014

By Bianca Foggiatto, Marko Hilden, Malcolm Powell

"Since the introduction of the concept of flexible circuits (Powell and Bye, 2009), it has been further developed and refined to the definition of ‚FlexiCircuits leverage ore variability to maximise resource utilisation?. The focus of flexible circuits is to investigate processing options that provide extra capacity through sophistication rather than scale. This requires a combination of smart ore characterisation, economic modelling and innovative processing plant design. Flexible circuit design can reduce energy requirements through gangue rejection or progressive ore upgrade; and increased robustness and controllability by leveraging off ore variation. Each rock type, as characterised through Geometallurgical ore modelling, may be processed more efficiently by individually optimising processing paths. The objective of FlexiCircuits is to transform the processing capability of comminution and concentrator plants - targeting step change in performance through integrating a range of interrelated improvement opportunities. Considerable effort has been applied to developing the modelling and simulations tools required to develop and demonstrate the potential of this concept. This paper presents a practical application as a test case. A realistic application of flexible circuits is provided through a conceptual circuit design of an iron ore processing plant. It is simulated as a multi-component feed with a range of new models in the researcher’s Model Developers’ Kit (MDK) to trial the ability of different circuit designs to respond to variable ore and quantifying the potential of these circuits to transform processing capability of variable ore feed. The outcomes of the simulations are presented and discussed, providing a practical demonstration of the level of modelling and simulation required and the potential of flexible circuit design."

Jan 1, 2014

By Sudhir Srivastava

India hosts a wide range of globally significant mineral resources, including four fuel minerals; 11 metallic minerals; 22 minor minerals and 52 non-metallic minerals. The country ranks among world?s top five nations for its commodity reserves of coal and iron ore. Interestingly, only small part of country's landmass has been explored that provides opportunity for future substantial mineral discoveries. India plans to double infrastructure investments to US$ 1trillion. Despite the challenges in infrastructure project implementation, mining sector remains a key driver of demand growth for commodities in the years to come with a good prospect to grow in future.

Sep 1, 2012

By Georg Unland, Thomas Wegner

"Impact crushers are widely used in different industries to crush materials which can vary from soft to hard and from ductile to brittle. However, the sizing of impact crushers is still based rather on empirical than on scientific approaches. Therefore, a test rotor was developed in order to investigate the principles of comminution by impact. Rocks of diabase with different diameters were used to gain the crushing properties with the following results:RESISTANCE AGAINST CRUSHINGLikelihood of BreakageThe likelihood of breakage is a function of the impact velocity and the particle diameter. The likelihood increases with higher velocities and larger diameters. Maximum Crushing ForceThe crushing force is related to the area of projection of the rock. The smaller the particles and the higher the velocities the larger are the maximum related contact forces.Contact TimeThe contact time increases with the rock diameter whereas the influence of the impact velocity is neglectable.Mass Specific Crushing WorkThe mass specific crushing work decreases with the particle diameter and increases with the impact velocity."

Jan 1, 2003

By S. A. Bogidaev, M. Yu. Tiunov

"The paper describes the results of the flotation tests with complex rare metal ores from deposits in the Trans-Baikal Territory. Correlations between the quality of produced wolframite, hubnerite and mica concentrates with or without the presence of various alkaline modifiers are determined. Commonly, rare metal ores contain minerals of comparable value to main elements recovered in processing plants using gravitational methods. The paper describes the results of flotation recovery of valuable minerals – main and associated – from gravity tailings of deposits in the Trans-Baikal Territory. It was found that gravity tailings from the first deposit contained fine-grained wolframite, mica (muscovite, lepidolite etc.), feldspar; hubnerite, scheelite, beryl, fluorite, rubidium-containing muscovite from the second deposit, correspondingly. This paper presents the results of the stage flotation tests with the production of tungsten (wolframite, hubnerite), fluorite and mica concentrates from gravity tailings. Figure 1 demonstrates the flowsheet of tungsten ore minerals and mica stage flotation from gravity tailings of the first deposit.Wolframite can be floated using oleic acid with the presence of soda ash, a complexing collector (IM-50), under slightly alkaline conditions in combination with a nonpolar collector [1, 2, 3, 4]. The study included wolframite flotation using the combination of two alkaline modifiers. Flotation of wolframite was performed after pulp desliming, using tall oil saponified with soda ash. The recovery of wolframite in the concentrate of rougher flotation reached 80-85%; the concentrate contained up to 1% of tungsten oxide that can be upgraded to a saleable product using gravitational methods. This procedure was tested during flotation of wolframite, tantalite-columbite and pyrochlore, and provided high performance regardless of a season, at pulp temperatures of 8-10°C, though fattyacid collectors are significantly inefficient at such low temperatures due to low solubility, dispersion and increased collector consumption, consequently. The introduction of two alkaline modifiers in pulp appears to improve these characteristics.The first stage of the tests was focused on increase of iron-bearing tungsten ore minerals recovery from gravity tailings and stabilization of the cold pulp flotation process."

Jan 1, 2018

By E. Kusaka, M. EL Salmawy

"The electrokinetic behavior of EL Maghara coal has been investigated in the presence of nonyl and octyl nonionic surfactants containing polyethoxy of different sizes with trade names of Triton-X100 (TX-100), Triton-X 705 (TX-705), Triton WR-1339 (TWR-1339) and Brij 58. The electrokinetic behavior was determined by zeta potential measurements. Zeta potential measurements were conducted by Laser-Doppler electrophoresis technique using zetamaster. The results show that the zeta potential of Egyptian coal varies with pH value, the hydrocarbon chain and number of ethoxy groups in the hydrophilic group of the surfactant. It was found that the polymeric surfactants reduce the negative values of zeta potential of coal. The shift of PZC of coal upon deashing appears to be closely relevant to silicate mineral removal."

Jan 1, 2014

By Choi Sang-Ken, Chung Hun-Saeng, Kim Byoung-Gon, Park Chong-Lyuck

Fine grinding of crystalline graphite was conducted using a dry attrition mill with a vacuum system to investigate the characteristics of size reduction. Low pressure and high temperature conditions in the grinding mill were found to greatly improve the efficiency of the size reduction of graphite. Natural flaky graphite of .100 mesh was ground into sub-micron sizes, then over 90% of the product were able to be reduced below 1?without disrupting their crystallinity in a short period of time. Reducing the atmospheric pressure in the grinding environment promotes the removal of chemical species such as oxygen and water molecules adsorbed on the graphite particle, resulting in effective size reduction while maintaining the crystallinity of graphite.

Jan 1, 2003

By Gorki Davila, Irineu Brum

"Brazil has large reserves of coal (32 billion tons) located predominantly in the south of the country. Despite the relative ease of exploitation, these resources have been underestimated as a source of energy. Currently the country's strategic planning aims to minimize the gap between coal and resources traditionally used in the Brazilian energy matrix. In this scenario the processing of Brazilian coal by flotation appears as a promising alternative, having been successful in mineral systems containing fine particles This paper aims to study the overall process of flotation for a specific Brazilian coal. The material used in this study consists of fine coal that is usually discarded as waste and deposited in the tailings dam. The objective is to recover carbonaceous matter and reduce the ash and contaminants grade. The variables analyzed were the influence of size particle, solids concentration in the pulp, the concentration of surfactants and frothers to be used. The results showed that it is possible, from a feed with around 65% of ashes, to obtain products with approximately 35% ashes with mass recoveries about 40%. The types of collector reagent and foaming employees result in different concentrates. This study also presents a preliminary analysis of the effect of water recovery in concentration parameters."

Jan 1, 2014

By R. Chowdhury

Axis House manufactures and supplies alkylhydroxamate reagent of various carbon chain lengths for application in flotation of oxide copper and other minerals. As part of reagent performance improvement the structural factors of hydroxamate are examined by various analytical tools in particular with X-ray diffraction of single crystals. In a recent publication, the structure of n-octylhydroxamic acid and its corresponding potassium salt are presented with findings of hydroxamic functional group geometric preference, H-bonding, keto-enol tautomerisation, acid-salt aggregation and alignment of carbon chain. In this paper an example of branched alkylhydroxamate 3, 5, 5-trimethylhexylhydroxamate will be presented and compared with the result of linear alkylhydroxamate.

Sep 1, 2012

By J. W. Ahn

Calcined calcium oxide from limestone is hydrated to manufacture calcium hydroxide, and then precipitated calcium carbonate is synthesized from calcium hydroxide. Precipitated calcium carbonate of various morphologies is obtained by controlled conditions of each step and characteristics of limestone, calcium oxide and calcium hydroxide. Especially characteristics of calcium hydroxide have the most influence on morphology of precipitated calcium carbonate character. In this study, therefore, it is investigated the specific surface area of calcium hydroxide and morphology of precipitated calcium carbonate according to hydration temperature. Calcium hydroxide hydrated at high initial temperature has larger particle size than that hydrated at low initial temperature. And formation yield of aragonite precipitated calcium carbonate has improved by using calcium hydroxide had larger particle size (hydrated at high initial temperature).

Jan 1, 2014

By Yuri Yemelianov, Stanislav Balikov, Alexander Epiforov, Andrey Boldyrev, Andrey Bogorodsky

"Test work was carried out using copper gold-bearing flotation concentrate with 6.85%Cu, 14.30%Fe, 20.70%S and 2.34%As. Gold and silver grade in the concentrate is 54.6 g/t and 92 g/t, respectively. Gold and copper are valuable components in the concentrate. Gold is partially associated with pyrite and fahlores. Copper in the concentrate can be found as tennantite (Cu12As4S13). The 71% of gold from the flotation concentrate is recoverable by cyanidation with simultaneous cyanide consumption in the amount of 96 kg/t. The major reason of refractoriness is that gold is fine encapsulated into sulfides and the presence of cyanicide-copper. The concentrate ground as much as 95% minus 10 µm was treated using low-temperature POX at the temperature of 100±5°C, L:S ratio of 5:1 and the process time of 1-5 hours. Residual sulfide sulfur in the cake is 2.28% which is 89% sulfide oxidation. The highest copper recovery to POX solution is 91%. It was found that gold recovery to cyanide solution is 85-94% during alkaline pre-treatment of POX cakes followed by cyanidation. In this case, cyanide and lime consumption is 75-90 kg/t and 120 kg/t, respectively. In order to recover precious metals from POX cakes leaching using sodium sulfite was carried out. Test work was conducted at varied reagent concentration, L:S ratio and leaching time. Gold and silver recovery achieved was 85-95% and 59-63%, respectively."

Jan 1, 2014

By R. ?. Sherembayeva, ?. ?. ?uktybayeva, ?. B. Rakhimbekova, N. ?. ?m?rova

"Studying the interaction of the phosphorus-containing flotation reagent with the components of the flotation system ""liquid-gas-solid"" during flotation of non-ferrous metal ores allows regulating the enrichment process. The phosphorus-containing reagent-collector anabasinium-O,O-dimethyl-thiophosphate has beensynthesized under laboratory conditions and the concentrated aqueous solution of anabasin hydrochloride and the 40% solution of sodium hydroxide have been used as the raw material. The phosphorus-containing reagent has been obtained by interaction of the anabasine base, sulfur and dimethyl phosphite, due to sulfur and nitrogen atoms it can form complex compounds with heavy metal ions.Studying flotation of copper-sulfide ore of the Sayak field with the use of the phosphorus-containing reagent-collector anabasinium has been performed in the open and closed cycles. The degree of ore grinding was 60- 62% of the class -0.074 mm. There has been established the dependence of the ore flotation parameters on: a) pH of the pulp; b) the consumption of the reagent-collector anabasinium.The effect of the pulp pH on the technological parameters of copper ore flotation has been carried out with a reagent regulator that increases the difference in the surface properties of the minerals to be separated.There has been used lime as the regulator of the medium, the consumption of which varied from 750 to 1500 g/t; the consumption of the reagent-collector anabasinium was 10, 15, 20 and 25 g/t.It has been found that when flotation of copper ore without the use of lime at pH equal to 7.8 and at the reagent consumption, g/t: anabasinium - 25, T-92 - 55, copper recovery in the concentrate is 92.72%, the quality of concentrate is 7, 1%.In flotation according to the factory mode (the consumption of xanthate is 44 g/t, T-92 is 55 g/t, pH = 7.8 (without lime)) of copper ore, copper recovery in the concentrate is 87.38%, the concentrate quality is 7, 97%, with reducing the xanthate consumption to 25 g/t copper recovery is reduced to 83.39%, the quality of the concentrate is up to 6.69%.In the experiments using the factory reagent mode in the closed cycle, with the xanthate mass consumption of 44 g/t, T-92 blowing agent of 55 g/t, the third recleaning concentrate contained 19.13% copper with recovery of 86.89%.Using a phosphorus-containing reagent instead of xanthate with the same flow rate, the third recleaning concentrate with the mass fraction of copper of 19.82% has beenobtained with recovery of 87.77%."

Jan 1, 2018

By Chanki Jeong, Heechan Cho

In this study, batch flotation experiments were conducted to recover rare earth elements (REE) from an REE ore deposit in the Mushgai Khudag area, Mongolia. Apatite was found to be the major REE mineral while monazite and xenomite were observed as minor minerals. The main purpose was to float apatite to increase the REE content. Oleic acid was used as collector and MIBC was used as frother. Sodium silicate was used as a depressant for iron compounds. NaOH was used to adjust the pH of the flotation to about 9.5~10.0. The particle size was 90% less than 152 ?m (- 100 mesh). The content of REE elements was analysed by ICP - OES to determine the contents of REE such as Ce, La, Nd, Pr and Y. When sodium silicate was used, the best result was obtained using 0.2 mL of sodium silicate, 2 mL of oleic acid and 2 mL of MIBC. Under these conditions, the recovery of REE was about 78% and the grade of the first froth product was 42,995 ppm Ce, 24,088 ppm La, 14,236 ppm Nd, 4,388 ppm Pr and 1,570 ppm Y. When conducting flotation after iron minerals were removed by magnetic separation, a better result was obtained; with 2 mL of oleic acid, 2 mL of MIBC and no sodium silicate, the recovery was increased to 90% and the grade was also increased to 58,600 ppm Ce, 28,624 ppm La, 17,160 ppm Nd, 5,348 ppm Pr and 1,971 ppm Y.

Jan 1, 2014

By C. H. Zhou

Cryogenic grinding of Printed Circuit Board will bring less pollution, reduce energy costs, smaller particles, regular particle size, efficient process, separation various materials due to different fracture toughness. Systemic studies of recycling discarded Printed Circuit Board (PCB) by low-temperature modification and cryogenic grinding have been made in this paper. Firstly test mechanical property of PCB at different low-temperature, including impact strength, flexural strength, and shear strength. Do experiment on the power consumption of different cooling temperature, The results show that the average power consumption is lower between -30? to -60? and the average power is decrease in evidence at -30?. Use ZKB type double roll shear crusher to crush PCB to 20mm×20mm particle size, in a temperature range of -10 ~ -30? Used R type mill to grind sample to minus 3mm under different working condition, the average power consumption is decrease in evidence from -10 ? to -30 ?, power consumption is the lest at rotational speed is 1180rpm.

Jan 1, 2014

By V. F. Petrov, E. P. Olberg, S. V. Petrov

"The study was carried out using process solutions produced during cyanidation of gold-bearing concentrates from a gold-processing plant. It was found that the water contained a significant portion of thiocyanate (7910.0 mg/L), cyanide was virtually not present. The metals occurred primarily as iron (355.0 mg/L) in the form of ferrocyanide. Cyanide recovery was conducted using an ozone treatment process with reactors developed by the Environmental Department of Irgiredmet. The process design ensured complete utilization (100%) of O3, thus equipment operation safety increased.The recovery of free cyanide from thiocyanate was 76.6%, which corresponded to 5.12 kg of NaCN (100%) per 1 m3 of solution. Recovered NaCN can be used for recycling in hydrometallurgical processes.The operating costs estimation showed that the production cost of a tonne of recovered cyanide was US$1288.7, considering the prices of energy and commercial sodium cyanide in Russia in 2017, i.e. recovered cyanide is cheaper than commercial cyanide by 55.8%.INTRODUCTION Depletion of oxidized gold-bearing ores readily amenable to cyanidation has shifted focus to large-scale processing of primary ores with high sulphide content. Primary ores processing flow sheets involve gravitational and/or flotation concentration with subsequent treatment of produced gold-bearing concentrates. Typically, concentrates reporting to cyanidation contain considerable amounts of sulphur that can interact with CN- and further formation of SCN-. The use of refractory gold liberation methods (bacterial liberation, ultra-fine grinding) provides activation of this side reaction up to complete consumption of free cyanide in a short period. This makes water recycling unviable and impractical.The interaction of the sulphur content in concentrates and cyanide contributes substantially to consumption of NaCN required for efficient gold recovery. Inappropriate consumption of the main reagent achieves dozens of kilogram per tonne of material to cyanidation, and reaches approximately 100% when gold is recovered from activated sulphide-containing products (e.g. by ultra-fine grinding)."

Jan 1, 2018

By Buks Kruger

"After the milling and flotation of the platinum bearing ore, the flotation concentrate is electrically smelted in 6-in-line electric arc furnaces and the resulting furnace matte treated in Peirce Smith converters to remove the iron sulphide. The iron free (less than 1% Fe) converter matte is then granulated and sent to the Base Metals- and Precious Metals Refineries for further processing.During the smelting and converting processes two distinct gas streams are produced.The Peirce Smith converter off gas contains 4% - 9% SO2 which is treated in a conventional Sulphuric Acid Plant to produce sulphuric acid (H2SO4).The electric furnace off gas contains 0.9% SO2 and was (until September 2002) vented through a 91 meter high stack to atmosphere.Off gasses which contain less than 3% SO2 is difficult to handle and quite a few processes had been developed over the years to cope with this gas. A broad spectrum of process suppliers and technology approaches is available and the different technologies can be divided into a few main approaches i.e.Scrubbing of the off gas with an alkaline solution to produce an environmentally friendly and stable waste product which can be discharged onto a tailings dam or permanent landfill site.Physical absorption of the SO2 into a chemical solution to produce high quality chemically pure process chemicals.Catalytic reaction of SO2 with O2 to produce SO3 which is absorbed in water to produce sulphuric acid of less than 90% strength.In October 2002 Impala Platinum commissioned a Sulfacid Plant at its Smelter in Rustenburg which recovers the SO2 from the electric furnace off gasses into a weak sulphuric acid solution.The Sulfacid Plant technology is widely used in the paint pigment industry. This is, however, the first application of the technology on electric furnace off gas.The furnace off gasses contains flue dust which is removed in electrostatic precipitators. The gas exiting the precipitators normally still contains between 40 mg/Nm3 and 60 mg/Nm3 dust and passes through a quench-scrubber before entering the reactors. The quench-scrubber cools the electric furnace offgas down from ± 200 °C to 60 °C and act as a final dust removal stage."

Jan 1, 2003

By V. Y. Dementyev

Laboratory and pilot-plant testing using a sample of gold-bearing semi-oxidized ore from a Russian deposit followed by a flow sheet and reagent flotation mode development to design a plant was carried out in IRGIREDMET in 2009-2010. According to the developed flow sheet low alkaline flotation conditions are recommended in order to activate the surface of sulfides. The pH lowering from natural (7.5-8.0) to optimal (4.6-4.8) value using sulfuric acid provides for an increase in gold recovery. Before CIL, a final flotation concentrate is pretreated using pressure oxidation. It was found that the use of recycled solutions from pressure liberation in order to create acidic conditions for flotation instead of sulfuric acid during pilot-plant testing is recommended. The flow sheet offers the detoxification of remaining pressure oxidation solutions together with the flotation tailings. The carbonates presented in the tailings significantly reduce the consumption of lime for detoxification and allows for the use of two tailings dams instead of three. The first is used for the tailings of flotation and pressure oxidation recycled solutions, which were detoxified together. The second tailings dam is used for detoxified cyanidation cakes of the flotation concentrate. It was found during pilot-plant testing that flotation under natural and acidic conditions provides for 88.9 percent and 93 percent gold recovery, respectively. 4.1Au percent increase recovery was achieved due to the reduction of gold losses with flotation tailings and better quality of concentrates.

Sep 1, 2012

By Kalle Härkki

Sustainability principles in the minerals industry are now becoming more and more important from the perspective of securing a license to operate and enhancing environmental, economic and social performance. This trend is also setting new challenges for the design and operation of future concentrator plants. It is evident that ore grades are declining and ores are becoming more complex requiring new technology innovations and holistic approach for process optimization. There is a demand for more energy-efficient process technologies especially in comminution that is the major energy consuming unit operation in the process chain. Energy is not only a major source of cost but also contributes significantly to the carbon and environmental footprint. There is also an increasing awareness that more intelligent water management is required for reduction of fresh water consumption and mastering the impacts of process water recycling will cause for process performance. In association with water recycling, tailings disposal is an integral part of concentrator plant representing significant environmental and economic issues to the operation. This presentation will discuss general trends and challenges of future minerals processing plants and how innovative technology solutions and better integration of unit processes in conjunction with intelligent process control would contribute to meeting the sustainability challenges.

Jan 1, 2014

By Lev O. Filippov, Inna V. Filippova

"Flotation of metal-organic precipitate in column is sensible to the hydrodynamic conditions determined by the diameter and dispersion of rising bubbles. Thus, the dissipation energy in the system resulting of ratio between superficial fluid velocities (gas and feed) in the column is main parameter for precipitate flotation in pilot or industrial scales. The knowledge of aggregate structure can lead to better understanding and control of many solid-liquid separation processes (sedimentation, filtration, thickening and flotation). Many authors highlight the importance of structural properties (i.e. floc density) for different industrial applications.This approach was applied to achieve the flotation of molybdenum precipitate obtained with organic collector a- benzoin oxime for molar ratio 1:2. Flotation tests were carried out at lab and pilot scale with rigorous control of the size distribution of bubbles and the values of dissipation energy in the systems.Structural evolution of Mo precipitate and the destruction phenomenon were described by using of the various fractal dimensions, which were deduced from experimental data of laser sizer devices and optic microscopy pictures of precipitate. The boundary fractal dimensions Df of large aggregates allows the detection of a structural scaled organisation of the precipitate flocs (elementary germs-microflocs-flocs). The fractal dimension of the particle mass distribution Dm=1.94+/-0.15 suggests, for the floc structure, a cluster-cluster aggregation process either with structuration or breakage phases.The destruction process characterised by a fractal dimension Dg controls the final size distribution. The floc destruction occurs for the lowest values of the dissipation energy (0.02 – 0.05 W/kg). The relation between Dg and the system dissipation energy Et (for various energy E dissipated in the agitation cell) involves the different breakage mechanisms of aggregates in function of the aggregation bonds (Fig. 1).Besides, the destruction of floc produces very fine particles (elementary germs or/and microfloc according to E), and thus induces the difficulties of bubble-particle attachment during the precipitate flotation in column. Yet, very small bubbles, which increase the collision probability, would make the flotation feed rate decrease. The optima ratio between superficial gas and feed velocities are determined for bubble size and flotation results control at pilot scale. Thus, it is possible to providing the catastrophically changes of precipitate column flotation by using the following established experimental relation: the mean diameter d of the flocs under the action of dissipated energy Et follows a power like law (d~Et -0.5). This allows estimating the size distribution of flocs for the E values which can appear in column."

Jan 1, 2003