Liquid-solid flotation

Liquid-solid distributions are involved in ion-exchange and other adsorption-based separation processes, separation processes based on crystallization or precipitation, flotation processes for ore dressing, and smelting processes. 

Voorhees s experimental study of low-volume-fraction-solid liquid+solid Pb-Sn mixtures carried out under microgravity conditions during a space shuttle flight enabled a wider range of solid-phase volume fractions to be studied without significant influence of buoyancy (flotation and sedimentation) effects [13]. The rate of approach to the steady-state particle-size distribution in 0.1-0.2 volume-fraction... 

FLOTATION. A method of separating minerals from waste rock nr solids of different kinds by agitating the pulverized mixture of solids with water, oil. and special chemicals that cause preferential welling of solid panicles of certain types by the oil. while other kinds are not wet. The unwelled particles arc carried to the surface by the air bubbles and thus separated from the wetted particles A frothing agent is also used to stabilize the bubbles In Ihe form of a froth that can be easily separated from the body of the liquid (froth flotation). Do not confuse with floatation. 

Gas-liquid bubble columns and gas-liquid-solid slurry bubble columns are widely used in the chemical and petrochemical industries for processes such as methanol synthesis, coal liquefaction, Fischer-Tropsch synthesis and separation methods such as solvent extraction and particle/gas flotation. The hydrodynamic behavior of gas-liquid bubble columns and gas-liquid-solid slurry bubble columns are of great importance for the design and scale-up of reactors. Although the hydrodynamics of the bubble and slurry bubble columns has been a subject of intensive research through experiments and computations, the flow structure quantification of complex multi-phase flows are still not well understood, especially in the three-dimensional region. In bubble and slurry bubble columns, the presence of gas bubbles plays an important role to induce appreciable liquid/solids mixing as well as mass transfer. The flows within these systems are divided into two... 

The aim of this investigation has been to set-up a real model for precipitate flotation which would comprise adsorption processes at both the aicdiquid and liquid-solid interfaces, as well as some elements of fluid mechanics. All the parameters in the model have been determined experimentally. The initial concentrations of both DBS and Cu(0H)2 in the experiment have been varied in parallel. Recoveries of the Rotated species have been determined in order to calculate their real and maximal (theoretical) values for the surface concentrations. Formation of the particle-bubble aggregates has been monitored by determining the number and diameter of both the particles and air bubbles. The collector adsorption in the flotation systems has been studied via recovery of DBS itself on air bubbles, as well as in the presence of Cu(0H)2. 

In the flotation processes 2 simultaneous adsorptions of DBS take place on the gas4iquid and liquid-solid interfaces. 

Ovhemical DOSING for improvement of liquid-solid separation is traditionally designed and operated more or less independently of the geometry and hydraulic performance of the actual separation reactor. The widespread use of jar tests in the day-to-day operation of filtration and flotation plants illustrates this fact. Yet it is not difficult to visualize situations in which aggregation processes would furnish floes unsuitable for the subsequent separation unit, such as voluminous floes that do not settle out readily. 

Suspensions treated under conditions in which good floe formation exist are separated with higher efficiency in flotation units. For intermediary conditions of floe formation, sedimentation in well-designed tanks B and C and flotation tank D show comparable overall efficiency in liquid-solid separation. Flotation appears to be less favored than sedimentation if floe formation is accomplished by lower chemical dosages. 

The use of flotation for liquid-solid separation may compensate for some of these limitations of the sedimentation process for suspensions with less optimal floe formation. This effect was observed in particular if suspensions were coagulated with Al3+. 

Surfactants are used in a wide variety of applications such as ore flotation, cleaning, polymerization processes, and pharmaceuticals and agriculture. The usual role for the surfactant is to modify interfacial properties, whether they be liquid/liquid, solid/liquid, or gas/liquid interfaces. To be effective in any of these applications, however, the surfactant must adsorb strongly at the interface. In addition to its concentration at the interface, the conformation of the surfactant at the interface is also an important factor. While the influence of solution properties such as concentration, ionic strength, and pH on surfactant adsorption are well known, the properties of the other phase also exert a significant influence. 

Ultrasonic Measurement. The ultrasonic determination of a sample s degree of crystallinity is based upon the observation that the speed of sound in a polyethylene sample is proportional to the sample density. The experimental arrangement requires a combined transducer/receiver, a flat sample, and a reflector to be immersed in a thermostated water bath. The transducer produces a train of pulses that are reflected from the various liquid/solid interfaces and recorded by the receiver, with and without the sample in place. From the time delay between the initial pulse and the various reflections it is possible to calculate the thickness of the sample and the speed of sound within it. The instrument must be calibrated with a series of known samples, the densities of which have been determined by an absolute method, i.e. flotation. 

Flotation. Flotation is a gravity separation process which exploits differences in the surface properties of particles. Gas bubbles are generated in a liquid and become attached to solid particles or immiscible liquid droplets, causing the particles or droplets to rise to the surface. This is used to separate mixtures of solid-solid particles and liquid-liquid mixtures of finely divided immiscible droplets. It is an important technique in mineral processing, where it is used to separate different types of ore. 

When used to separate solid-solid mixtures, the material is ground to a particle size small enough to liberate particles of the chemical species to be recovered. The mixture of solid particles is then dispersed in the flotation medium, which is usually water. Gas bubbles become attached to the solid particles, thereby allowing them to float to the surface of the liquid. The solid partices are collected from the surface by an overflow weir or mechanical scraper. The separation of the solid particles depends on the different species having different surface properties such that one species is preferentially attached to the bubbles. A number of chemicals are added to the flotation medium to meet the various requirements of the flotation process ... 

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