Flotation Essay

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During flotation, water phase is enriched in gas bubbles which adhere to the oil droplets. This causes an increase to the buoyancy of the oil droplets and provokes a faster motion to the surface of water. Due to the gas, a foam layer is formed in the surface in which the oil droplets get trapped and then removed. This process is used mainly for oil droplets of size smaller than 10 microns and high levels of 90%+ oil removal can be achieved. A gas flotation vessel is shown in figure xx. Water enters the recirculation header and then is guided to eductors. During the flow, water is enriched in gas bubbles through a nozzle. Then flotation is caused due to bubbles in the chamber and foam is formed in the froth which in the end of the process is …show more content…

Coalescence is provoked by the different velocities between the droplets which leads to collissions. Eventually coalescence is dependent on the kinetic energy of the droplets and the attractive or repulsive forces acting between them. During coalescence the droplet size increases and that makes easier the separation of them from the surrounding phase. In the event of high interfacial tension, coalescence is decisive since the droplets will accumulate close to the interphase. The energy input to the system should by low enough to permit the coalescence process. In case of high energy inputs, dispersion will occur. On the other hand the energy input should be high enough to promote frequent droplets collision or else the whole process will proceed at a very low pace. In most treating vessels coalescence is depending on gravital forces. Flotation units and hydrocyclones are an exception to this rule. Those vessels are nicknamed as the ''deep bed gravity settlers'' (Maurice et al.2009). Experiments conducted with those vessels show that there is only a 10% size increase in the droplets if residence time is doubled and that the more dilute is the oil the greater is the residence time needed. In other words after a certain time of coalescence in the vessel, additional retention time has small …show more content…

They can be easily differentiated visually. The main focus of the present work is water-in-oil emulsions which appear as dirty oily water. They can contain different oil types and in various concentrations. Depending on the industry fats, cutting fluids, lubricants, tars, crude oils and grease can be found. In order to extract them from water hexane, carbon tetrachloride, fluocarbons or chloroform can be used. Apart from the oil, various contaminants can be present in emulsions such as solids, metal particles, soaps, silt and

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