To make coal and oil power plants cleaner, they need to remove sulfur from the gases they produce. To do this, they use FGD (Flue Gas Desulfurization) technology that requires measuring the density of limestone in real-time. Some technologies that measure this density use nuclear isotopes, which can be complicated and subject to government regulations. Rhosonics density analyzers offer a simpler and cheaper solution that avoids problems with other types of sensors. These sensors work well even when there are complex flow paths, blockages, or erosion.
Have a look at the SDM Slurry Density Meter. This model is regularly used for slurries that cointain in limestone. Rhosonics instruments monitor the attenuation with ultrasonic signals, of which the density can be measured directly and in-line.