flotation process

Flotation Process One of the most employed methods for concentrating minerals is the called flotation process which makes a physiochemical separation whereby an ore is ground to produce slurry which is then subjected to mixing and very fine bubbles of air are formed into the slurry in order to carry the valuable mine rals. It is possible that precious minerals which have been liberated from non-precious metals during the grinding step attach to the bubbles and rise to the surface to form a rich froth that can be skimmed to form a product called concentrate. The poss ibil ity of sepa ratin g vari ous substanc es by usin g a flota tion process is opened up due to the several changes which can be done on the surfaces minerals with the assistance of chemical reagents which make the valuable particle s hydrophobic. These are called collectors. Through physiochemical adsorption they are attached with the ends of the molecules at the surface. The adsorption of the collector could be influenced by adding other reagents which can be either supportive or inhibitive in effect. In these cases is common to make reference to activators and depressants. Air is added to move the hydrophobic particles to the surface of the slu rry und er agita tio n. Fur the r rea gen ts must be add ed in ord er to fac ili tate the adherence of particles to the bubbles and which hold in a layer of froth the particles which have displaced to the water-air interface. These reagents are called frother and can be natural or synthetic. The flo tation is done by fol lowi ng several ste ps: conditionin g of the slu rry wi th appropriate reagents, injection of finely disseminated air bubbles through the slurry, collection of valuable particles on the bubble surfaces and inert rock remaining in suspension, and removal of the mineralized froth and discharge of the unwanted mineral. Analysis of flotation process is best approach through considerati on of the overall process first, and then of its components. An ideal system would be a circuit in a steady state, supplied at a constant rate with ore having constant initial properties, a fixed optimum size distribution and its mineral surfaces pretreated to yield optimum floatability. The feed would flow through machines and circuits selected, designed, and adjusted to give an optimum separation, resulting in production of concentrates at a fixed rate and grade, and with an associated recover y. In order to do reality a flotation process is necessary to carry out flotation tests at the lab. Also, the tests are a powerful tool for improving an existent process and do a pri mar y evaluati on about some pos sible cha nge s such as rea gen ts, aer ati on, cleaning steps and regrinding. Most of tests are done in laboratory flotation cells with 500 to 4000 grams of ore. All the data obtained can be used in optimizing the dosage of reagents and retention times in industrial cells. In the basic research is common use small cells such as Hallimond tube and micro flotation cell. Industrial flotation is practiced in the called flotation machines. Although many different machines are currently being manufactured and many more have been developed and discarde d in the past, it is fair to state that two distinct groups have arisen; pneumatic and mechanical machine s. The type of machine is t he great importance in designing a flotation plant and is frequently the characteristic causing most debate.

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Flotation Process

One of the most employed methods for concentrating minerals is the called flotationprocess which makes a physiochemical separation whereby an ore is ground toproduce slurry which is then subjected to mixing and very fine bubbles of air areformed into the slurry in order to carry the valuable minerals. It is possible thatprecious minerals which have been liberated from non-precious metals during thegrinding step attach to the bubbles and rise to the surface to form a rich froth that canbe skimmed to form a product called concentrate.

The possibility of separating various substances by using a flotation process isopened up due to the several changes which can be done on the surfaces mineralswith the assistance of chemical reagents which make the valuable particleshydrophobic. These are called collectors. Through physiochemical adsorption theyare attached with the ends of the molecules at the surface. The adsorption of thecollector could be influenced by adding other reagents which can be either supportiveor inhibitive in effect. In these cases is common to make reference to activators anddepressants. Air is added to move the hydrophobic particles to the surface of theslurry under agitation. Further reagents must be added in order to facilitate theadherence of particles to the bubbles and which hold in a layer of froth the particleswhich have displaced to the water-air interface. These reagents are called frother and can be natural or synthetic.

The flotation is done by following several steps: conditioning of the slurry withappropriate reagents, injection of finely disseminated air bubbles through the slurry,collection of valuable particles on the bubble surfaces and inert rock remaining insuspension, and removal of the mineralized froth and discharge of the unwantedmineral.

Analysis of flotation process is best approach through consideration of the overallprocess first, and then of its components. An ideal system would be a circuit in asteady state, supplied at a constant rate with ore having constant initial properties, afixed optimum size distribution and its mineral surfaces pretreated to yield optimumfloatability. The feed would flow through machines and circuits selected, designed,and adjusted to give an optimum separation, resulting in production of concentratesat a fixed rate and grade, and with an associated recovery.

In order to do reality a flotation process is necessary to carry out flotation tests at thelab. Also, the tests are a powerful tool for improving an existent process and do aprimary evaluation about some possible changes such as reagents, aeration,cleaning steps and regrinding. Most of tests are done in laboratory flotation cells with500 to 4000 grams of ore. All the data obtained can be used in optimizing the dosageof reagents and retention times in industrial cells. In the basic research is commonuse small cells such as Hallimond tube and micro flotation cell.

Industrial flotation is practiced in the called flotation machines. Although manydifferent machines are currently being manufactured and many more have beendeveloped and discarded in the past, it is fair to state that two distinct groups havearisen; pneumatic and mechanical machines. The type of machine is the greatimportance in designing a flotation plant and is frequently the characteristic causingmost debate.