Effects of Coal Composition and Flotation Reagents on the Water Resistance of Binderless Briquettes

Abstract

The difference in the physical properties, particularly the water resistance or wet strength, of the binderless coal briquettes produced from flotation feed and concentrate was investigated using six bituminous coals from two collieries in the Witbank Coalfield. The coal samples were analyzed for their proximate, petrographic, and mineralogical properties. The presence, in the flotation concentrates, of the reagents used during the froth flotation process was also investigated using gas chromatography.

Pillow-shaped binderless briquettes were produced from coal samples at various moisture contents and a pressure of approximately 17 Mpa using a Komarek B-100A double-roll press. The briquettes were tested for some physical properties (i.e., dry- and wet-compressive strengths), which were thereafter compared with the properties determined for the coal samples.

The binderless briquettes produced from the flotation concentrates were more water-resistant than those produced from the flotation feed. The flotation feed and concentrates of the coals tested were found to have similar petrographic properties. As expected, the ash and kaolinite contents were found to be lower in the flotation concentrates than in the flotation feed. Flotation reagents were detected in the flotation concentrates from both collieries. From the results obtained it is concluded that the increased water resistance of the binderless briquettes produced from flotation concentrates of the coals tested is due to a combination of the fineness of the coal particles, assisted by the amount of reactive macerals (most particularly vitrinite) with the lower ash and kaolinite contents, together with the presence of the flotation reagents, particularly the collector, in the flotation concentrate.

Keywords:

• Binderless briquetting
• Coal
• Flotation reagents
• Macerals
• Mineral matter

This work was part of Task 4.4.1 of the Coaltech 2020 research program (a South African collaborative mining research initiative – http://coaltech.csir.co.za) that is gratefully acknowledged for permission to publish the work. The constructive criticism and contribution of Dr. Ricky Pinheiro is also gratefully acknowledged.

Notes

^#Total reactive macerals = vitrinite + liptinite + reactive inertinite.