The role of hydrocarbon oils in coal flotation : an investigation in to some pulp phase sub-processes

Oil dispersion, oil adsorption (including selectivity), and the influence of oil on bubble creation and attachment were studied, in an attempt to explain observed differences in flotation behaviour with -500 μm unbeneficiated bituminous coal. Collectors were synthesis grade and commercial stocks of aromatic and aliphatic oils; MIBC was the frother. Oil dispersions were analyzed using a Coulter Counter. All the oils were sufficiently dispersed for effective flotation, with aromatic oils being better dispersed. MIBC usually hindered oil dispersion. The kinetics and extent of oil adsorption onto solids were monitored with a specially developed technique. Aromatic oils adsorbed extensively (90 ) on the coal but aliphatic oils adsorbed far less. Nevertheless this was sufficient to render coal particles floatable. All the oils were highly selective. MIBC did not promote oil adsorption. Bubbles were electronically scaled and counted. Aromatic oils reduced bubble size markedly. Their spontaneous spreading at the air-water interface is associated with a net lowering of interfacial tensions. Aliphatic oils do not spread and consequently had little influence on bubble size. Bubble size is an important contributory factor to froth stability and oils which reduce sizes are better collectors. MIBC reduced bubble size (as expected): in combination with one commercial oil, sizes were reduced below those induced in the presence of either reagent in isolation. Coal recovery was largely dependent on froth stability since oil dispersion and adsorption was adequate. The mode of conditioning was important at low reagent dosages; as was the mode of reagent addition. Oils should be predispersed prior to addition to the pulp to facilitate their distribution. MIBC, which is preferentially oil-soluble should be added to the pulp separately and as late as possible to ensure maximum frothing activity. In the absence of extraneous surfactants, the pulp-phase behaviour of MIBC and oil is well understood and was invariably able to explain the observed flotation performance satisfactorily. Interfacial theory, which was reviewed in some detail, is currently inadequate for predictive purposes and empirical tests will remain necessary for the foreseeable future.

Grantor dc:publisher.institution

Department of Chemical Engineering

Year dc:date.issued

1988

Author dc:creator

• Anderson, Guy Victor Murie

Advisor dc:contributor.advisor

• Franzidis, Jean-Paul

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/8377

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/8377