A fundamental study of the selective hydrophobic coagulation process

It has been found that naturally hydrophobic carbonaceous materials such as coal and graphite can be selectively coagulated and separated from hydrophilic impurities without the use of oily agglomerants, flocculants or electrolytes. The coagulation occurs at ζ-potentials significantly higher than those predicted by the classical DLVO theory, suggesting that it is driven by a hydrophobic interaction energy. Thus, the process is referred to as the selective hydrophobic coagulation (SHe) process. The fundamental development of this process is the focus of this study. In this study, the energy barriers for the coagulation of two different coal samples and a graphite sample have been calculated using the extended DLVO theory, which incorporates the hydrophobic interaction energy in addition to the dispersion and the electrostatic energies. Stability diagrams have been developed from the data, which show that the maximum ζ-potential at which a given coal can coagulate decreases as surface hydrophobicity decreases. For the coagulation of minerals present in coal, the classical DLVO theory has been used for the energy barrier calculations. The results of these calculations provide an excellent correlation with the results from a series of SHC tests conducted with run-of-mine coal. The strength of the coal aggregates have also been investigated by measuring the coagula size distributions under different hydrodynamic conditions. The coagula size distributions were measured using an in-situ particle size analyzer. These results have been used along with models for coagulation rate and breakage rate to determine strength characteristics of the aggregates and to verify the primary parameters controlling the aggregate size. The study found that the coal and graphite aggregates incurred a substantial reduction in size when a small amount of mechanical agitation was applied. Based on this outcome, quiescent continuous processes have been successfully designed and developed to separate the coagulated hydrophobic particles from the dispersed hydrophilic particles.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Mining and Minerals Engineering

Department dc:contributor.department

Mining and Minerals Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1992

Author dc:creator

• Honaker, Ricky Quay

Chairs dc:contributor.committeechair

• Luttrell, Gerald H.
• Yoon, Roe-Hoan

Committee members dc:contributor.committeemember

• Adel, Gregory T.
• Wheeler, Thelma D.
• Karmis, Michael E.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-06062008-165559

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/38333