Combined effect of natural dispersant and a stabilizer in formulation of high concentration coal water slurry: Experimental and rheological modeling

The current investigation involves the formulation and stabilization of high concentration coal-water slurry using a sub-bituminous bimodal coal sample and a dispersant derived from Acacia auriculiformis plant in presence of stabilizer carboxyl methyl cellulose. We have first time studied the surface activity of natural surfactant A. auriculiformis isolated by chemical and aqueous extraction method by calculating their critical micellar concentration (CMC) on the basis of surface tension measurement. CMC of isolated dispersant was found to be 0.021 g/cm3 and 0.010 g/cm3 for aqueous and chemical extraction method respectively. Four different sizes of coarse particles such as 217–295 μm, 97–295 μm, 155–217 μm, and 80–145 μm were mixed with fine particle size of below 37 μm to form bimodal coal samples of Sa-1, Sa-2, Sa-3, and Sa-4, respectively. The apparent viscosity of the coal water slurry was investigated as a function of coal particle size variation, different coarse to fine ratio of coal particle, concentration of coal in the range (60–67.2%), A. auriculiformis concentration in the range (0.01–0.021 g/cm3) and stabilizer concentration (0.001–0.01 g/cm3). The addition of carboxymethyl cellulose as stabilizer increased the coal concentration and durability of the slurry. The effect of functional group of surfactant has been discussed in establishing the mechanism of stabilization of coal water slurry. A theoretical simulation approach has been given to justify the experimental observation.