The agglomeration of coal fines using wet microalgae biomass




Scenedesmus, Coalgae®; pellets


South African coal generally contains a high percentage of non-carbon mineral matter, which necessitates processing to remove the bulk of the non-carbon material. Such processing results in the formation of some 60 million tons of discard coal and between four and eight million tons of very fine, unusable coal, called ultra-fines, each year. The objective of this study was to investigate factors that impact on the agglomeration of fine coal of <150 mm when using microalgae biomass as the sole binder. Mixtures of coal and wet microalgae biomass were prepared and pelletised. The proximate properties of the mixtures and coal were determined and the physical properties of the pellets measured, such as compression strength, water resistance and impact resistance. The results showed that pelletisation of Coalgae® is a promising technology for the recovery of coal fines. Moisture content, pressure and holding time influence the quality of the pellets. Compression resistance testing indicated that pellets made from the coal80%-algae20% (by weight) mixture were stronger than those made from the coal90%-algae10% (by weight) mixture. Pellets made from samples with ± 17% moisture content exhibited the strongest resistance, one of 1.8 kg/mm2 for the coal80%-algae20% mixture that was centrifuged after 24 hours. The water resistance index for all the pellets was lower than the recommended 95%, which was considered to put emphasis on handling, transportation and storage of the pellets.


Download data is not yet available.


Metrics Loading ...

Author Biography

Sibongiseni Gloria Gaqa, Nelson Mandela University

Department of Chemistry (InnoVenton)


ASTM_D2013: Standard method of preparing coal samples for analysis.

ASTM_D3173: Standard test method for moisture in the analysis sample of coal and coke.

ASTM_D3175: Standard test method for volatile matter in the analysis sample of coal and coke.

ASTM_D3172: Standard practice for proximate analysis of coal and coke.

ASTM_D3174: Standard test method for ash in the analysis sample of coal and coke.

Cai, J., He, Y., Yu X., Banks S. W., Yang, Y., Zhang, X., Yu, Y., Liu, R. and Bridgwater, A. V. 2017. Review of physicochemical properties and analytical characterisation of lignocellulosic biomass. Renewable and Sustainable Energy Reviews, 76, 309–322.

Diez, M.A., Alvarez, R. and Cimadevilla, J.L.G. 2013. Briquetting of carbon-containing wastes from steelmaking for metallurgical coke production. Fuel, 114, 216–223.

Easby W. 1848. Method of converting fine coal into solid lumps. United States patent office. Patent No. 5,739.

Gaqa S., Mamphweli S., Katwire D. and Meyer E. 2014. The properties and suitability of various biomass/coal blends for co-gasification purposes. Journal of Sustainable Bioenergy Systems, 175–182.

Hancox, P.J. and Götz, A.E. 2014. South Africa’s coalfields — A 2014 perspective. International Journal of Coal Geology, 132, 170–254.

NREL/TP-510-42621: Sluiter A., Hames B., Hyman D., Payne C., Ruiz R., Scarlata C., Sluiter J., Templeton D. and Wolfe J. 2008. Biomass and Total Dissolved Solids in Liquid Process Samples.

Parikh, J., Channiwala, S. and Ghosal, G. 2005. A correlation for calculating HHV from proximate analysis of solid fuels. Fuel, 84(5), 487–494.

Parikh, J., Channiwala, S. and Ghosal, G. 2005. A correlation for calculating HHV from proximate analysis of solid fuels. Fuel, 84(5), 487–494.

RIchards S.R. 1990. Physical testing of fuel briquettes. Fuel Processing Technology. 25, 89-100.

South Africa River Energy, 2013. The formation of River Energy SA, 38–40.

Saikia, M. and Baruah, D. 2013. Analysis of physical properties of biomass briquettes prepared by wet briquetting method. International Journal of Engineering Research 6(5), 12–14.

World Energy Council. 2013. Technical Report, Energy efficiency technologies Annex 1 – Energy efficiency potentials and barriers for realisation in the industry sector.

Zeelie B., (Nelson Mandela Metropolitan University) 2013. Upgrading coal fines using microalgae. South Africa Patent Application, 2013/03681.




How to Cite

Gaqa, S. G., & Watts, P. (2018). The agglomeration of coal fines using wet microalgae biomass. Journal of Energy in Southern Africa, 29(2), 43–50.