Measurement of the rheology of distillers' grain slurries using a helical impeller viscometer

Currently, research and development is being conducted to improve the economic value of distillers' grains, the bottoms product of corn dry mill ethanol distillation. Little is known about the flow behavior of distillers' grains. The rheological properties of distillers' grains were examined in this study.; Distillers' grain slurries are non-Newtonian, heterogeneous fluids subject to particle settling. Traditional methods of viscosity measurement, such as cone and plate and concentric cylinder are not adequate in determining rheological properties of these fluids. A helical impeller viscometer was employed to accurately measure impeller torque over a range of rotational speeds.; Newtonian and non-Newtonian calibration fluids were utilized to obtain constants that relate shear stresses and shear rates to the experimental data. Newtonian calibration fluids were used to determine the impeller constant, c, while non-Newtonian calibration fluids were used to calculate the shear rate constant, k. The calculated average impeller constant was 151. The average shear rate constant calculated was 10.3.; Distillers' grain slurries of 21, 23, and 25 percent solids concentration were examined using the helical impeller method. The rheological behavior of the slurries was fit to three empirical viscosity models: power law, Herschel-Bulkley, and Casson models. Regression coefficient (R2) ranges for each model were: 0.9925–0.9995 (power law), 0.9977–0.9996 (Herschel-Bulkley), and 0.9970–0.9977 (Casson). The power law and Casson empirical models were adequate methods for modeling rheological behavior of distillers' grain slurries of concentrations between 21 and 25 percent solids.