Effects of initial slurry concentration distribution on the particle size distribution measured with a sedimentation balance method

We investigated the effects of the initial concentration distribution of slurry in a sedimentation bath on measuring the size distribution with a sedimentation balance method. As a result, when the initial slurry concentration around the upper free surface is lower than the other lower parts, the acquired value of the cumulative undersize in the coarse size range is evaluated to be smaller than the true value. It is found that the error of the cumulative undersize value in the coarse range increases as the measured particle size increases. The flow field of the dispersion medium and the motions of particles in it were simulated numerically. Consequently, the convection flow of the medium gives the error in the fine range and the mass median diameter of smaller powder remarkably well. The equations which express the change in the sedimentation mass were revised when the initial slurry is not distributed uniformly. Accurate size distribution of monodisperse powder can be acquired and the error in the size distribution of polydisperse powder is reduced by these revised equations even when the initial slurry concentration distribution is not uniform.