Wet grinding of CaCO3 with a stirred media mill: Influence of obtained particle size distributions on pressure filtration properties

Abstract

Chemical and process industries utilize stirred media mills for efficient fine grinding of solids. Stirred media mills, also referred to as stirred ball or stirred bead mills, generally have a good ability to produce fine particles with a relatively narrow particle size distribution. Wet grinding with vertical stirred ball mills is typically carried out for slurries containing particles smaller than 200 μm, such as industrial minerals and pigments. Filtration is an important unit operation, which is performed in order to reduce the water content of the slurry after grinding and concentration, and prior to drying and transportation. Pressure filters are used to obtain the maximum dryness of the product. A number of properties of solids affect the filtration performance. The particle size and shape, the width of particle size distribution, and the net surface charge of the particles are among the factors having a significant influence on the filtration characteristics.

In this study, the dependency of the pressure filtration properties of wet ground calcium carbonate (GCC) slurries on the grinding result obtained by a stirred media mill is investigated. After grinding, subsequent filtration experiments were carried out with a laboratory-scale pressure filter. Average specific cake resistances, porosities of the filter cakes, and cake compressibility parameters were determined from the filtration data. The results showed clear correlations between the particle size data and the related filtration properties. Interesting observations were also made regarding the average porosity of the filter cakes and the uncertainty of the experiments.