Abstract

O. EJESIEME, Vitus et al. Reclamation of ultra-fine coal with Scenedesmus microalgae and comprehensive combustion property of the Coalgae® composite. J. energy South. Afr. [online]. 2020, vol.31, n.1, pp.14-27. ISSN 2413-3051.  http://dx.doi.org/10.17159/2413-3051/2020/v31i1a6430.

Combustion of South African discard ultra-fine coal, charcoal, microalgae biomass, and composites of the three under air were studied. The objective of the study was to determine the effect of Scenedesmus microalgae biomass on the comprehensive combustion characteristics (CCC) of the ultra-fines. The composites were designed with Design Expert and, unlike blending with the dry microalgae biomass, fresh slurry was blended with the ultra-fine coal and charcoal. Non-isothermal combustion was carried out at heating rate of 15 °C/min at 40-900 °C and flow rate of 20 ml/min, oxygen/ carbon dioxide (O2/CO2) air. Combustion properties of composites were determined from thermogravimetric-differential thermogravimetric analysis and analysed using multiple regression. On combustion, the interaction of coal-charcoal-microalgae was antagonistic (b = -1069.49), while coal-microalgae (b = 39.17), and coal-charcoal (b = 80.37), were synergistic (p = 0.0061). The coal-mi-croalgae (Coalgae) indicated first order reaction mechanism, unlike coal and the charcoal. The CCC index of Coalgae, (S-value = 4.52E8) was superior relative to ultra-fine (S-value = 3.16E8), which indicated high-quality fuel. This approach to combusting ultra-fine coal with microalgae biomass is partly renewable, and it would advance the production of heat and electricity. HIGHLIGHTS: • Scenedesmus added value to reclamation and combustion of ultra-fine coal. • The interaction between coal dust and microalgae biomass was synergistic. • The derived response surface model could predict comprehensive combustion characteristics. • The combustion kinetic model of Coalgae deviated from first order reaction.

Keywords : kinetics; modelling; optimisation; s-value; synergistic.

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