Particle-Particle Interactions in Sub-Bituminous Coal Powder Agglomerates: Surface Thermodynamic Approach

Abstract

This paper presents particle-particle interactions in sub-bituminous coal powder agglomerates employing surface thermodynamics approach. The coal was ground in a dry state with a milling machine into powder form and sieved with Octagon 2000 sieve shaker of size range 75m - 850m. The coal powder (0.01404kg) was mixed with about 1.3cm3 of 50% ethanol which served as a binder. Also the binding forces of agglomerates were determined with the binding force model. The Lucas-washburn equation was used to determine the contact angle (θ = 64.8˚) of sub-bituminous coal. 0.0361Jm-2 and 0.0324Jm-2 were determined as the surface energy and interfacial tension of sub-bituminous coal respectively. The values of Hamaker coefficient in a medium A131 = 1.201×10-20Jouls was obtained using the values of surface tension of binder, contact angle, Neumann equation, MATLAB fzero command and combination rule. The positive value of Hamaker coefficient, which implies net positive van der Waals forces shows an attraction between two particles. The outcome of this study would improv fugitive dust control, decrease transportation losses and lower risk of spontaneous combustion of coal agglomerates. The theory of van der Waals effect was successfully applied to the study of particle-particle interactions in the agglomeration of coal.