| A number of experiments were conducted to determine the flotation characteristics of Iowa coals in which various conditions were applied to study the effect of different parameters such as frother dosage, oily collectors, pyrite depressants, and various combinations of these reagents. Flotation tests were also conducted with Appalachian coals for comparison.;Appalachian coals floated rapidly with only a frother (methyl isobutyl carbinol) or an alkaline solution. A small amount of an oily collector increased the recovery of Appalachian coals significantly. The results of these flotation experiments showed that little mineral matter was removed when a high recovery was achieved. A microscopic analysis of Appalachian coal used in these experiments showed that much of the mineral matter was incompletely liberated from the coal particles. And, the use of ultrasonics did seem to improve mineral matter liberation.;Bubble-particle attachment was studied from a theoretical view point. This study showed that the mechanism of attachment differs depending on the relative size of bubbles and particles. When small bubbles adhere to a flat or slightly curved surface of a particle, the bubble size was found to be determined by the contact angle between the bubble and the particle. The study indicated that micro-bubbles could separate mineral matter from low rank coal more selectively than macro-bubbles could. When a micro-bubble flotation technique was employed to float Appalachian coal, it produced a cleaner coal product than conventional macro-bubble flotation.;A general kinetic model was proposed to represent the rate of flotation of coal. For two Appalachian coals, the model successfully represented the flotation kinetics of uniformly sized coal. The proposed model also represented well the flotation kinetics of coal consisting of two sizes of particles.;Iowa coals did not respond as well to froth flotation as Appalachian coals. Although Iowa coal floated very slowly and incompletely with only a frother (methyl isobutyl carbinol or MIBC), it floated rapidly when a large dosage of an oily collector (No. 200 LLS fuel oil) was employed in addition. No. 1 fuel oil was not nearly as effective as a collector for this application. The order of addition of flotation reagents appeared very important for achieving a high recovery of Iowa coal. |
