Conventional Flotation Circuit Research Articles

Effect of hydrogen peroxide on selective flotation of chalcocite and enargite

Enargite is typically associated with chalcocite. Owing to the similarity in the flotation behaviors of these minerals, both minerals are reported to concentrate in the conventional flotation circuit. However, inorganic arsenic in enargite can decrease the copper concentrate quality and increase the operating cost of processing this concentrate. Separating these minerals is important for cleaner copper production to avoid these effects. In this context, this study investigated the effect of hydrogen peroxide (H2O2) treatment on the flotation behavior of chalcocite and enargite. Flotation tests of pure and mixed minerals indicated that H2O2 treatment reduced the floatability of chalcocite and enargite by forming sulfate and copper hydroxide on their surfaces. Despite the detrimental effect of the H2O2 treatment, there was a narrow window of H2O2 concentration for separating both minerals, in which enargite floated and chalcocite was depressed. This selective flotation behavior was caused by the rapid adsorption of potassium amyl xanthate (KAX) and lower surface oxidation of enargite compared with that of chalcocite.

Agglomeration–Flotation of Finely Ground Chalcopyrite Using Emulsified Oil Stabilized by Emulsifiers: Implications for Porphyry Copper Ore Flotation

Flotation is the conventional method for processing porphyry copper deposits, one of the most economically important sources of copper (Cu) worldwide. The rapidly decreasing grade of this type of Cu ore in recent years, however, presents serious problems with fine particle recovery using conventional flotation circuits. This low recovery could be attributed to the low collision efficiency of fine particles and air bubbles during flotation. To improve collision efficiency and flotation recovery, agglomeration of finely ground chalcopyrite (CuFeS2) (D50 = 3.5 μm) using emulsified oil stabilized by emulsifiers was elucidated in this study. Specifically, the effects of various types of anionic (sodium dodecyl sulfate (SDS), potassium amyl xanthate (KAX)), cationic (dodecyl amine acetate (DAA)), and non-ionic (polysorbate 20 (Tween 20)) emulsifiers on emulsified oil stability and agglomeration–flotation efficiency were investigated. When emulsifiers were added, the average size of agglomerates increased, resulting in higher Cu recovery during flotation. This dramatic improvement in flotation efficiency could be attributed to the smaller oil droplet size in emulsified oil and their higher stability in the presence of emulsifiers. The utilization of emulsifiers during agglomeration–flotation not only lowered the required agitation strength for agglomeration but also shortened the agglomeration time, both of which made the process easier to incorporate in existing flotation circuits.

Selective separation of chalcopyrite from pyrite with a novel non-hazardous biodegradable depressant

Pyrite depression in copper ore flotation often requires large doses of inorganic depressants that lead to high toxicity, high costs, and low selectivity. Thus, this study offers a novel pyrite depressant, polyglutamic acid (PGA), in the selective flotation of chalcopyrite with xanthate as a collector. The flotation and adsorption mechanism on chalcopyrite and pyrite were systematically studied using a series of flotation tests, zeta potential measurements, adsorption analysis, infrared spectral (IR) analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The addition of PGA depressed the flotation of pyrite more strongly than chalcopyrite in the wide pH range of 8–12. In the presence of PGA, selective separation between the two minerals was achieved at pH 9, and the recovery of chalcopyrite was over 85% and that of pyrite was less than 20%. All of the surface analysis techniques indicated that PGA interacted differently with the two minerals and the surface of pyrite adsorbed a much greater amount of PGA than that of chalcopyrite. Prior addition of PGA significantly reduced the adsorption of the collector on the pyrite surface and thus depressed its flotation. However, the significant adsorption of the collector and its oxidation to dixanthogen on the chalcopyrite surface caused its improved flotation even in the presence of PGA. Therefore, PGA, which is a non-hazardous, biodegradable, and renewable reagent, could be used as an alternative pyrite depressant in Cu–Fe conventional flotation circuits.

The effect of rotor speed on the flash flotation performance of Au and Cu in an industrial concentrator

Improvement in the performance of a flash flotation cell can be achieved through optimisation of the cells flotation/classification profile via the manipulation of process operating variables such as feed rate, feed per cent solids, rotor speed and dual outlet flow. This paper presents the findings of changing the rotor speed on the internal hydrodynamics and valuable element (Au and Cu) performances in an industrial flash flotation cell.Two survey campaigns have been conducted on a 1200 tph flash flotation cell to assess the effect of changing rotor frequency (and consequently RPM) on the performance of the cell. Four rotor settings were tested during this work: 45, 50, 55 and 60 Hz. During the first campaign a survey was taken after the flash flotation cell had achieved stable operation for approximately 2 h at each frequency setting; with 50 Hz representative of the normal operation of the machine. The Au recovery results from this initial campaign identified 55 Hz as the optimal setting for the rotor frequency. The second survey campaign was performed to confirm the base case results (50 Hz) and reassess the 55 Hz case after the machine had operated at this frequency for 48 h. The unit recovery of Au and Cu increased by 39% and 28% respectively at the optimised frequency, with a notable increase in the recovery of coarser Au (+150 μm) which is readily recoverable by the downstream gravity devices.A comparison of the cyclone overflow stream (conventional flotation circuit feed) has shown that when the flash flotation cell is operating in the optimised state, there is a shift in the distribution of Au by size being sent to the conventional flotation circuit. There is a relative 8% increase in the amount of Au within the optimal size range (+20/−150 μm) for flotation recovery, which should therefore increase the overall Au recovery in the conventional flotation circuit. Follow-up analysis of plant data has shown that the final tail Au grade from the conventional flotation circuit has decreased by an average of 0.0235 ± 0.0129 g/t to 0.179 g/t, and that this decrease is statistically relevant at a 95% confidence level.The effect of rotor speed on the internal flow regime of the cell has been demonstrated through the use of axial profile data and profile normalisation. This has allowed a visual representation of the effect of increasing power input into the slurry and the consequent changes to turbulent flow. How this impacts both the internal classification profile of the machine and the size based performances of the target elements (Au and Cu) is discussed in detail. 3D interpretation of the effect of rotor speed on the size based recovery of Au and Cu within the machine are presented, and are the first such representations to be made for real data obtained from within an operating industrial scale flash flotation machine.

The role of a flash flotation circuit in an industrial refractory gold concentrator

In order to determine the contribution of the flash flotation circuit to the overall plant performance of the Kanowna Belle concentrator, two survey campaigns both with and without the flash circuit in operation have been conducted on two distinctly different ore types: a very high grade ore, and a very low grade ore of higher hardness. Using two different ores with the same target valuable mineral species (gold and pyrite) through the same treatment route allows any trends in performance to be more easily identified. As both survey campaigns involved running the plant with and without the flash flotation circuit in operation, the significant contribution of the flash flotation cell to overall plant recovery and final concentrate grade is highlighted. The flash circuit on this plant may be considered as the primary rougher, contributing in excess of 42% of the valuable material that is recovered to the final concentrate stream, at a grade of approximately 35% sulphur; and in-so-doing reducing the overall plant footprint that would otherwise be required to achieve the same recoveries at the target concentrate grade.Mineralogical analysis of survey samples shows that the feed to the flash flotation cell (cyclone underflow) is of a much higher grade and contains a higher proportion of well liberated valuable material as compared to the conventional flotation circuit feed (cyclone overflow). Maximising the recovery of this material before it re-enters the milling circuit should be of paramount importance to optimising overall plant performance.When the flash flotation circuit is taken off-line the recovery of sulphur (and hence pyrite) is observed to decrease dramatically, and whilst the recovery of gold also decreases, it is to a much lesser extent. The difference in the recoveries of gold and pyrite that is observed without the flash flotation circuit in operation is most likely attributable to a change in the way the gold is being liberated as a function of the change in grinding circuit operation that is required when the flash circuit is taken off-line. The distribution of valuable material in the cyclone overflow stream (conventional flotation feed) undergoes a step change when the flash circuit is taken off-line with an increase in the amount of valuable fines being generated, which is further reflected in the flotation tails with a higher proportion of both pyrite and gold being present in the intermediate and fine size classes. This increase in the amount of pyrite fines in particular may have contributed to the loss in recovery that was observed when the flash flotation circuit was taken off-line.Pulp chemistry data from various points around the flotation circuit highlight the different processing conditions in the flash cell, compared to the conventional circuit, which will impact on the type of minerals able to be recovered by flotation, as well as reagent selection for this type of processing application.

The JK three-product cyclone—performance and potential applications

In spite of their wide application in comminution circuits, hydrocyclones have at least one significant disadvantage in that their operation inherently tends to return the fine denser liberated minerals to the grinding mill. This results in unnecessary overgrinding which adds to the milling cost and can adversely affect the efficiency of downstream processes. In an attempt to solve this problem, a three-product cyclone has been developed at the Julius Kruttschnitt Mineral Research Centre (JKMRC) to generate a second overflow in which the fine dense liberated minerals can be selectively concentrated for further treatment. In this paper, the design and operation of the three-product cyclone are described. The influence of the length of the second vortex finder on the performance of a 150-mm unit treating a mixture of magnetite and silica is investigated. Conventional cyclone tests were also conducted under similar conditions. Using the operational performance data of the three-product and conventional cyclones, it is shown that by optimising the length of the second vortex finder, the amount of fine dense mineral particles that reports to the three-product cyclone underflow can be reduced. In addition, the three-product cyclone can be used to generate middlings stream that may be more suitable for flash flotation than the conventional cyclone underflow, or alternatively, could be classified with a microscreen to separate the valuables from the gangue. At the same time, a fines stream having similar properties to those of the conventional overflow can be obtained. Hence, if the middlings stream was used as feed for flash flotation or microscreening, the fines stream could be used in lieu of the conventional overflow without compromising the feed requirements for the conventional flotation circuit. Some of the other potential applications of the new cyclone are described.

Dynamic modelling and advanced multivariable control of conventional flotation circuits

Expert and predictive multivariable control algorithms for a conventional copper flotation circuit were assessed through simulations. These simulations were carried out with a nonlinear dynamic model, derived from mass balances and empirical relationships, that qualitatively reproduced the dynamic behaviour of a real plant well. In order to make the simulations more realistic, they included noisy measurements, stochastic parameter variations and input disturbances. New expert algorithms were able to keep the plant operating within a pre-defined zone for long periods without complete control saturation, unlike previous expert controllers. In addition, the inclusion of constraints in a multivariable predictive algorithm verified improved control system regulation and flexibility.

Column Flotation at the Middle Fork Preparation Facility

Abstract A laboratory and pilot-scale test program was carried out to assess the merits of installing column flotation cells at the Middle Fork coal preparation facility. The test data showed that column cell technology was superior to single- and multi-stage conventional flotation circuits in terms of fine coal recovery and product grade. In light of these promising results, a full-scale column flotation circuit was designed, installed and commissioned at the Middle pork plant. The circuit utilizes five 3-m diameter Microcel™ flotation columns to process approximately 100 tph of minus 150 μm raw coal. The column retrofit reduced the ash content of the plant's flotation circuit by nearly 7 percentage points and increased the combustible recovery by approximately 27 percent. This article provides a summary of the test results and discusses the scale-up procedures used to design the commercial columns.

Evaluation of the recovery of liberated and unliberated chalcopyrite by flotation columns in a copper cleaner circuit

The behaviour of chalcopyrite in flotation columns in a copper cleaner circuit was evaluated by an image analysis and materials balancing technique to compare chalcopyrite recoveries by cleaner columns with chalcopyrite recovery by conventional cleaner flotation cells. A higher recovery of free chalcopyrite grains smaller than 10 μm was obtained by the column flotation circuit than by the conventional flotation circuit. It was also observed that pyrite and sphalerite particles smaller than 13.3 μm are entrained in the Cu concentrates from both the column and conventional flotation circuits.