Elsevier

Minerals Engineering

Volume 16, Issue 4, April 2003, Pages 399-401
Minerals Engineering

Technical Note
Comparison of non-ionic and ionic collectors in the flotation of coal fines

https://doi.org/10.1016/S0892-6875(03)00047-5Get rights and content

Abstract

Some ionic collectors were used as an alternative to conventional non-ionic collectors to obtain clean concentrates from fine coal samples containing 46.1% ash. Mixtures of kerosene and pine oil were used as conventional reagents while commercial fatty acids were used as ionic collectors. Flotation results showed that conventional collectors could not reduce the ash content of concentrate below 21.0% whereas, ionic collectors were found significantly better at reducing the ash content down to 16%, but their yields were lower.

Introduction

Owing to natural hydrophobicity, many coals may be easily floated with only a frother and fuel oil is often necessary to increase the yield. But, non-conventional reagents have been found very effective in the flotation of low-rank oxidized coals. Aplan and Arnold (1991) found ionic reagents (tributyl phosphate, carboxylic acids, and amines) better collectors in the flotation of low-rank oxidized coals. Recently, Jia et al. (2000) showed that a series of non-ionic surfactants, tetrahydrofuryl butyrate, were more effective collectors than oily collector dodecane for both oxidized and unoxidized coals. In addition to the degree of oxidation, coal’s response to flotation also varies with ash and carbon content. With regard to ash content, the greater the ash content, the less hydrophobic is the coal since silicates and other ash-forming minerals are readily wetted by water and cause slime coatings on coal particles.

In this research, non-ionic and ionic reagents were used as collectors to obtain clean concentrates from high ash coal fines. The reagents were compared in terms of flotation yield and ash content of the concentrates. The flotation mechanism of different reagents and their effectiveness as collectors were discussed.

Section snippets

Materials and methods

Minus 0.5 mm size coal fines of Zonguldak Coal Washery (in Turkey) were sampled before entering thickener. The samples were first allowed to settle, decanted and then dried at 60 °C. Ash analysis carried out according to ASTM D 3174-73 standard showed that the sample contains 46.1% ash.

Kerosene and pine oil were used as conventional reagents while tall oil, Pamak 1, and Pamak 4 were used as non-conventional ionic flotation collectors. The ionic surfactants composed of fatty acids contain more

Flotation with conventional reagents

Coal samples were first floated by using 40–320 g/t of pine oil alone. The results are given in Fig. 1 in which performance of the reagents are compared in terms of concentrate ash and flotation yield. The concentrate with the highest ash (25.1%) and lowest yield (37.2%) was obtained at the lowest reagent dosage and the ash could not be reduced below 19.3% at any reagent dosage. It is considered that, at very low reagents dosage, the strength of the air bubble was so weak due to the

Conclusions

Despite their lower flotation yield and higher consumptions, ionic collectors can be used successfully in coal flotation where cleaner concentrates are required from high ash coal fines. Oily collector, kerosene, increased the yield and ash content of concentrates due to the entrapment of ash-forming materials within coal agglomerates formed by bridging action of collector. Collectors containing more than 40% oleic acid resulted in higher flotation yield than oleic acid alone for the same

References (4)

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