Abstract The agitation intensity has a directly influence on flotation performance, lifting the particles and promoting the contact of bubbles and particles. In this paper, the energy input by the agitation on apatite flotation was investigated. The influence of pulp agitation in the flotation rate of particles with different sizes and two dosage levels was evaluated by batch testing. The flotation tests were conducted in an oscillating grid flotation cell (OGC), developed to promote a near isotropic turbulence environment. The cell is able to control the intensity of agitation and measure the energy transferred to the pulp phase. A sample of pure apatite was crushed (P80=310µm), characterized and floated with sodium oleate as collector. Four levels of energy dissipation, from 0.1 to 2 kWm-3, and two levels of collector dosage are used during the tests. The flotation kinetics by particle size were determined in function of the energy transferred. The results show a strong influence of the agitation intensity on the apatite flotation rate with both low and high dosage. For fine particles, when increasing the energy input, the flotation rate increase too, and this fact can be attributed to elevation of bubble-particle collisions. The kinetic result for the coarse particles demonstrated a reduction of the flotation rate whenever the energy input for this particle size was increased, whereby the turbulence caused by the agitation promotes the detachment of bubble-particle.

Abstract The current work presents a bibliometric discussion on articles published worldwide concerning kaolinite flotation in international journals from 1992 to 2015. In total, 39 articles were selected from Elsevier's database, SciVerse ScienceDirect. This work allowed to recognize and identify which are the thematic and methodological trends that are being used, in addition to the main collectors used in kaolinite flotation. The results show that a significant amount of articles is produced by Chinese authors, especially from 2013, as China is the second highest aluminum producer in the world, and kaolinite is the reject in the reverse flotation process of diaspore. The results showed the difficulty of working with kaolinite flotation individually and confirmed that there is scientific collaboration among authors. Bibliometric analysis showed that the reagents used in kaolinite flotation tests are mostly derived from cationic nitrogenated compounds. Additionally, best recovery results from kaolinite flotation occurred in acidic media.

Abstract Beneficiation of manganese ores has been conducted around the world by circuits composed basically of crushing, screening and spiral classifier. Therefore, solely the coarse size fractions (and commonly the richest) are actually recovered: "lump" (-75+9mm) and "sinter feed" (-9+0.15mm). In the industrial plant which processes the ore from the Azul Mine-PA, the overflow of the spiral classifier (- 0.15mm) is disposed of in a tailings dam because it bears a low Mn content (<10%) and high kaolinite content (70%). This paper reports the findings of a process development conducted on laboratory scale with the aim of concentrating Mn-bearing minerals from the tailings of the Azul Mine-PA (7% of Mn and 70% of kaolinite). The process is composed of desliming (-10µm), followed by reverse cationic flotation of kaolinite (rougher, scavenger) at pH~5. Results indicate that the reverse cationic flotation in the acid medium, when utilizing amide amine as collector and in the presence of a silicate activator and a dispersing agent could be a possible route for the concentration of tailings that had previously been deslimed at 10µm. The results yielded a mass recovery of 18%, a metallurgical recovery of 50% and a 32% Mn concentrate which may be mixed with current high grade products, increasing the overall recovery of the plant.

Nove amostras de minerais de ferro, provenientes de diferentes minas (jazidas) pertencentes à Vale, foram o objeto desse trabalho, que buscou correlacionar a depressão das referidas amostras com amido e carboximetil celulose versus parâmetros mineralógicos e morfológicos. O amido de milho convencional se mostrou capaz de realizar ação depressora sobre todas as amostras, exceto sobre aquelas que se mostraram mais ricas em hematita compacta (HC). Tais hematitas podem ser chamadas de "problemáticas", visto que interagem fortemente com o coletor e apresentam deficiência de serem deprimidas pelo amido, exigindo elevadas dosagens para minimização de sua tendência à flotação. Carboximetil celulose não apresentou ação depressora sobre nenhuma das amostras estudadas. A flotabilidade das amostras ricas em HC pode ser minimizada pela ação do amido de milho condicionado em pH 8,0-8,5. Testes de flotação com minério itabirítico, contendo elevado percentual de hematitas compactas de pequeno tamanho de cristal, confirmaram a redução do teor de Fe no rejeito com a utilização de amido condicionado em pH≅8.

Nine samples of Fe-bearing minerals from several mines of Vale were the object of this work, which aimed to make a correlation between mineralogy and morphology versus flotation depression by starch and carboxy methyl cellulose. They did not demand strong action from depressants. Cornstarch was able to depress all the samples, except those that exhibited high HC content. The latter samples could be regarded as "problematic" because they were able to interact strongly with collector and demanded a high dosage of depressant to accomplish full depression. Carboxy methylcellulose did not show depressive action on any of the studied Fe-bearing minerals. Flotation response of the samples, which are rich in HC, could be minimized by the action of starch conditioned at pH 8.0-8.5, increasing Fe recovery in the process.

O objetivo desse trabalho é apresentar e discutir a determinação dos parâmetros de dispersão de ar em células mecânicas de flotação, em circuitos industriais brasileiros. Foram investigados os circuitos rougher e scavenger das usinas RPM, Taquari-Vassouras, Copebras e Fosfértil-Catalão (atual Vale Fertilizantes). Nas usinas RPM e Taquari-Vassouras, foram determinados a velocidade superficial do ar (Jg), o hold-up do ar (εg), o diâmetro médio de bolhas (d32) e o fluxo de área superficial de bolhas (Sb). Para as outras usinas, foram determinados somente o Jg e εg. Os resultados mostraram que, com exceção da RPM, todos os circuitos investigados apresentaram baixos valores para os parâmetros de dispersão do ar. Taquari-Vassouras apresentou os mais baixos valores médios para Jg e εg, respectivamente, 0,05 cm/s e 5%. Os maiores valores de Jg foram determinados no circuito rougher da Copebras, 1,17 cm/s, ao passo que a RPM apresentou os maiores valores para o hold-up e tamanho de bolha, respectivamente, 31% e 2,61mm. Os valores obtidos, para Sb, situaram-se abaixo daqueles reportados na literatura.

The aim of this paper is to present and discuss the air dispersion parameters determined for industrial Brazilian flotation circuits. The rougher and scavenger circuits of RPM, Taquari-Vassouras, Copebras and Fosfertil-Catalão (today Vale Fertilizantes) were investigated. For RPM and Taquari-Vassouras, the superficial gas velocity (Jg), gas hold-up (εg), bubble size diameter (d32) and superficial area bubble flux (Sb) were measured, whereas only the Jg and εg were measured in the other circuits. The results pointed out that, except for RPM, all the circuits presented very low values for the air dispersion parameters. Taquari-Vassouras presented the lowest values for average Jg and gas hold-up: 0.05 cm/s and 5%, respectively. The highest Jg value was presented for the rougher circuit of Copebras, 1.17cm/s, while RPM presented the highest values for εg and bubble size, respectively 31% and 2.61mm. In the circuits where the calculation of the Sb parameter was possible, the results obtained lay in a range lower than those reported in literature.

Os processos básicos que governam a recuperação de partículas em uma célula de flotação compreendem os consecutivos subprocessos de colisão, adesão e estabilidade do agregado partícula/bolha. Entre eles, a colisão é controlada pelo ambiente hidrodinâmico na célula de flotação, enquanto que a adesão é dominada pelo comportamento físico-químico da interface entre partícula e bolha. Por sua vez, a eficiência da estabilidade depende, tanto dos eventos hidrodinâmicos, como dos físico-químicos. A recuperação de partículas grossas de apatita (densidade 3,08 g/cm³) e esferas de vidro (densidade 2,48 g/cm³) foi medida através de ensaios de microflotação e flotação em escala de bancada, variando-se diferentes parâmetros hidrodinâmicos na célula, como rotação e geometria do impelidor e números adimensionais (Reynolds & Froude). Os resultados indicam que velocidades apropriadas do impelidor produziram níveis de turbulência capazes de manter as partículas em completa suspensão, otimizando, assim, a eficiência de colisão entre partículas e bolhas, sem prejudicar a estabilidade dos agregados.

The processes that govern the rate of particle recovery in a flotation cell include the following sub-processes: collision, attachment, and stability of the aggregate formed by particles and bubbles. Collision is controlled by bulk hydrodynamics inside the flotation cell, while attachment is largely dominated by variables that belong to the domain of surface chemistry (contact angle, induction time). As for the stability of the particle/bubble aggregate, its efficiency depends on both hydrodynamics plus surface chemistry variables of the system. The flotation recovery of coarse particles of apatite and glass spheres was measured by micro-flotation and batch flotation tests in which hydrodynamic parameters were evaluated, such as impeller rotational speed, diameter, and geometry, as well as particle size and density. Results revealed that a proper impeller rotational speed yielded turbulence levels, which enabled to keep particles fully suspended, this way optimizing the collision efficiency between particles and bubbles, without jeopardizing the stability of the particle-bubble aggregates.

Esse trabalho faz revisão dos princípios utilizados por três importantes técnicas utilizadas para dimensionar espessadores: Fluxo de Sólidos, Talmadge-Fitch e Roberts. Elas foram aplicadas para validar o cálculo do diâmetro (D) e a área de sedimentação (A) de um espessador que clarifica salmoura em uma fábrica localizada em Cubatão-SP. O dimensionamento do espessador (cálculo de A e D) foi baseado no comportamento da sedimentação, avaliado em escala de laboratório, de partículas de sal suspensas em salmoura. Os valores de D e A (D=13,9-14,1m; A=151,7-156,1m²) obtidos pelas três técnicas foram comparados com o diâmetro do espessador real (D=20,0m). Por outro lado, os valores corrigidos para D e A (D=18,1-18,3m; A=257,0-263,0m²) foram obtidos usando um fator de escala (f =1,30). Esses valores são 10% menores em relação ao equipamento industrial.

This work reviews the fundamentals of three important techniques currently used to dimension thickeners: Flux of Solids, Talmadge-Fitch, and Roberts. They were applied to validate the calculation of diameter (D) and sedimentation area (A) of a real thickener, which clarifies brine in a plant located at Cubatão-SP. The calculation of thickener dimension (A and D) was based on the sedimentation behavior of salt particles in brine on a laboratory scale. The values of D and A (D=13,9-14,1m; A=151,7-156,1m²), which were calculated by the three techniques, were compared with the diameter of the real equipment (D=20,0m). On the other hand, corrected values of D and A (D=18,1-18,3m; A=257,0-263,0m²) were obtained by using a scale factor (f=1,3). These results are 10% lower than the real equipment.

A capacidade de bombeamento de rotores pode ser expressa em função de sua vazão de bombeamento (Qb) ou de seu número de bombeamento (N Q). Ambos parâmetros são muito úteis na caracterização hidrodinâmica de células mecânicas de flotação. Nesse trabalho, utilizou-se o micromolinete, para determinar Qb, N Q e, também, a velocidade de escoamento da água (v b), na descarga do sistema rotor/estator de uma célula Denver, modelo de laboratório. Em sua faixa de trabalho (900rpm<N<1400rpm), tanto na ausência, como na presença de ar, tal equipamento operou com v b=20-30 cm/s, Qb=298-454 cm³/s e N Q~0,06. O valor de N Q do modelo de laboratório exibiu valor muito próximo ao de uma célula industrial (N Q~0,05). Tal constatação indica que N Q pode ser útil no escalonamento de equipamentos. A presença de ar no sistema se mostrou capaz de diminuir a magnitude, tanto de v b, quanto de Qb, mormente na situação em que o rotor operou em rotações (N) mais elevadas. A perda de capacidade de bombeamento se deve ao fato de que tais células são do tipo sub-aeradas, onde o ar é introduzido no sistema através de vácuo gerado pela rotação do rotor.

The ability of impellers to produce bulk fluid flow may be expressed by the impeller flow rate (Qb) or the pumping number (N Q). Both parameters are very useful to characterize the hydrodynamics of mechanical flotation cells. In this work, an apparatus composed of a micromolen attached to an optic sensor was used to determine the impeller's water flow velocity (v b), Qb and N Q of a Denver laboratory flotation cell from the Laboratory of Mineral Processing, University of São Paulo. Under usual working conditions (1,100-1,300 rpm), in the presence and absence of air, the equipment operates at v b=20-30 cm/s, Qb=298-454 cm³/s e N Q~0,05. The value of N Q related to a laboratory cell was similar to an industrial one (N Q~0.05). Since Denver cells are sub-aerated, the presence of air in the system decreased the magnitude of v b and Qb when the impeller operated under higher rotational speed.

Muitos estudos acadêmicos foram realizados nos Estados Unidos, durante as décadas de 30 e 40, motivados pela correlação entre o estado de agregação da polpa e a recuperação do processo de flotação, observada no dia-a-dia das usinas. O objetivo desse trabalho é contribuir para uma maior compreensão do fenômeno observado na prática, dentro da realidade brasileira. Ensaios de microflotação e grau de dispersão foram realizados com partículas de quartzo, apatita e calcita. Os resultados reforçam a afirmativa postulada por Taggart e colaboradores de que a agregação ocorre como efeito da ação de reagentes e não como a causa de uma boa flotabilidade.

Many academic studies were carried out in the United States during the 1930's and 1940's, motivated by the correlation between the pulp aggregation state and the recovery at the flotation process, observed in industrial circuits. The aim of this work is to contribute to a better understanding of the phenomenon within the Brazilian reality. Microflotation and dispersion tests were carried out with quartz, apatite and calcite particles. The results strengthen the assertion by Taggart and co-workers that the aggregation occurs in the pulp as an effect of the reagents action and not as the primary cause of good flotability.

A técnica denominada Distribuição dos Tempos de Residência (DTR) constitui em um instrumento largamente utilizado pela indústria mineral, para estimar a qualidade da mistura que ocorre dentro das células de flotação. A técnica consiste em adicionar um traçador na entrada das células, controlando sua concentração na saída. Os resultados da aplicação dessa técnica são: a função DTR, o tempo médio de residência (t m) e a variância (s²). Esse trabalho apresenta e discute a aplicação da técnica DTR nas células mecânicas de flotação da Rio Paracatu Mineração, localizada em Paracatu-MG. Os resultados indicaram quais células operavam em melhores ou piores condições de mistura.

The Residence-Time Distribution (RTD) technique is a tool widely used in the mineral industry for assessing the mixture quality found in flotation cells. It involves introducing a tracer pulse at the feed of the cell and controlling the tracer concentration at its discharge. This technique provides the RTD function and the mean residence time (t m) and variance (s²). This work presents and discusses the application of the RTD technique on mechanical flotation cells of the Rio Paracatu Mineração, Paracatu-MG. The results provided technical guidance towards which cells operate in better or worse mixing conditions.