Influence of crystallization conditions on crystal morphology and size of CaCO₃ and their effect on pressure filtration

Abstract

The temperature, supersaturation, seeding procedure, stirring speed and other parameters were varied in crystallization experiments of calcium carbonate performed in aqueous solutions to control size, particle size distribution and morphology of the particles. Particle size information was obtained by focused beam reflectance measurements and the Coulter Counter Multisizer. Crystals of CaCO₃ could be crystallized as spherical polycrystalline particles of the vaterite polymorph, needle-like crystals of aragonite and both cube-like and novel plate-like crystals of calcite. Filtration experiments for calcium carbonate, performed at a constant pressure difference of 2 bar, show that spherical particles with a larger size show better filterability and that spheres with a wider size distribution, as a result of high supersaturation and nucleation, give higher average cake resistance values. Comparing different particle morphologies, plate-like crystals and needle-like crystals show worse filterability than spherical particles and cube-like particles. © 2011 American Institute of Chemical Engineers AIChE J, 2012