Froth flotation technique

Two bituminous coals of moderate ash content were chosen for this paper to illustrate this method of determining coal-mineral association. The first sample was an Upper Freeport coal with 1.3% moisture, 9.88% ash, and 1.56% total sulfur. The second sample was an Indiana No. 3 coal having 10.5% moisture, 7.35% ash, and 4.26% total sulfur. Both coals had been precleaned at a coarse particle size, ground to minus 325 mesh (44 ym), and then separate samples were cleaned by float-sink and by froth flotation techniques, as described elsewhere [5]. Analyses of the feed coals are included in Table I. 

Froth flotation is used to raise the low mineral concentrations in ores to concentrations that can be more economically processed. A concentration of 25-30% is suitable for economical smelting of copper. The froth flotation technique was originally developed in about 1910 to raise the copper concentrations of the strip-mined ores of Bingham Canyon, near Salt Lake City [9], and was further perfected for the differential separation of lead, zinc, and iron sulfides at Trail, B.C., at about the same time [10]. Flotation technologies are now widely used for separations such as the beneficiation of low grade Florida phosphate ores from 30-40% to 60-70% concentrations of calcium phosphate (BPL), and the separation of about 98% potassium chloride from sylvinite, a natural mixture of potassium and sodium chlorides. It is also used for bitumen separation from tar sand, removal of slate from coal, and removal of ink from repulped paper stock preparatory to the manufacture of recycled paper stock. More details of these separations are discussed in the relevant chapters. 

The Thoron method has been used for determining Th in plants [97], monazite sands and concentrates [9,30,31,98,99], silicate minerals [4,8,100], ores [101], zirconium minerals [49], and lanthanide compounds [42,44,102]. The froth flotation technique has been applied in the separation of Th from monazite sands [99],... 

After that, the residue is carried by conveyor belt to an air classifier. A stream of air is blown through the classifier, which has a zig-zag 20 shape. Low density materials such as plastic, paper, and some organic substances rise to the top of the classifier. Higher density materials such as glass and non-ferrous metals fall to the bottom and are discarded. These could be further separated out using a range of processes. For example, an eddy current mechanism 25 could screen out aluminium waste. Froth flotation techniques could recover glass. 

An advanced froth flotation technique called columm flotation has been shown to be superior in obtaining a low-ash clean coal with high recovery of combustible. It has been proved effective in recovering ultra-fine (minus 74 microns) coal. A schematic diagram of the column flotation process is shown in Fig. 17.13. 

Gravity concentration, ie, the separation of ore from gangue based on the differences in specific gravities, using jigs, heavy—medium separators, or spiral concentrators for example, is appHcable for lead ores. However, the predominant beneficiation technique used in modem plants is the bubble or froth flotation (qv) process (4,5). 

Although froth flotation is recognized as the best available fine coal cleaning technique, it becomes iueffective when the particle size is much smaller than 0.1 mm or when the feed contains a large amount of clay, resulting iu low coal recovery or poor selectivity. A solution to these problems is the use of modified flotation devices. 

Systems Separated Some of the various separations reported in the literature are listed in Rubin and Gaden, Foam Separation, in Schoen (ed.). New Chemical Engineering Separation Techniques, Interscience, New York, 1962, chap. 5 Lemlich, Ind. Eng. Chem., 60(10), 16 (1968) Pushkarev, Egorov, and Khrustalev, Clarification andDeactiva-tion of Waste Waters by Frothing Flotation, in Russian, Atomizdat, Moscow, 1969 Kuskin and Golman, Flotation of Ions and Molecules, in Russian, Nedra, Moscow, 1971 Lemlich (ed.), Adsorptive Bubble... 

Froth-flotation is an extensively used separation technique, having a wide range of applications in the minerals processing industries and other industries. It can be used for particles in the size range from 50 to 400 //m. 

Separation of milled solid materials is usually based on differences in their physical properties. Of the various techniques to obtain ore concentrates, those of froth flotation and agglomeration exploit differences in surface activities, which in many cases appear to involve the formation of complexes at the surface of the mineral particles. Separation by froth flotation (Figure 4) depends upon conversion of water-wetted (hydrophilic) solids to nonwetted (hydrophobic) ones which are transported in an oil-based froth leaving the undesired materials (gangue) in an aqueous slurry which is drawn off from the bottom of the separator. The selective conversion of the ore particles to hydrophobic materials involves the adsorption of compounds which are usually referred to as collectors. 4... 

Tin(IV) oxide is mined from naturally-occurring cassiterite. Various techniques are employed in mining (See Tin). The ore is crushed, ground, and separated hy gravity concentration and froth flotation. Sulfide impurities are removed hy roasting the ore concentrates at high temperatures. 

By using selective wetting agents, froth flotation is a possible separation technique. Acetic acid, methanol and quebracho can be used as selective wetting agents. All of these compounds are potentially selective provided the particle size of the polymers are similar. 

Materials mined from a mineral deposit usually consist of a heterogeneous mixture of solid phases that are generally crystalline and contain various minerals. Crushing and grinding operations are used to liberate the mineral species from one another and to reduce the size of the solids to a range suitable for subsequent processing. Of the various separation techniques, those of froth flotation and agglomeration exploit the chemical and physical properties of the surfaces of minerals, which can be controlled by various chemical interactions with species in an aqueous phase. 

With decreasing particle size, the practical feasibility of gravity separation diminishes because the efficiency of separation is reduced. Particularly in low-volatile coals, a substantial proportion of the coal may be lost in these fines if other means are not applied for separating them from the slime (clay) and recovering them. Froth flotation is one technique that is used for this purpose. 

Most of the Pu in seawater is not in solution but is adsorbed on suspended sediment. When waves break at the sea surface, the spray is enriched in sediment, and in Pu, relative to the bulk seawater, by a mechanism which is the basis of the technique of froth flotation used by chemical engineers to extract small particles from aqueous suspensions. 137Cs, being in solution in the seawater, is not enriched relative to Na in the spray. 

For separation of coal from relatively coarse shale and pyrite, gravity-based techniques have been effectively utilized. For sizes below 300 micrometers to about 100 micrometers, froth flotation has been used satisfactorily for separating coal from shales (3.). Even separation of pyrite from coal has been achieved by flotation (k). However, most of these processes become less effective when the particle size of the coal suspension is significantly below 100 micrometers. 

The purification and refinement operations can be batch or continuous. The raw blue is crushed and ground, slurried in warm water, then filtered and washed to remove the sulfoxides. Reslurrying and wet grinding release the sulfurous impurities and reduce the ultramarine particle size, often to 0.1-10.0 pm. The impurities are floated off by boiling or cold froth flotation, analogous to techniques used in the mining industry. 

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