TITLE:
Agglomeration Mechanisms and Kinetics during the Carbonation of a Suspension of Lime in a Pilot Batch Reactor
AUTHORS:
Mathilde Schnebelen, Kevin Mozet, Alexandra Jakob, Didier Sy, Edouard Plasari, Hervé Muhr
KEYWORDS:
Calcium Carbonate, Agglomeration Kernel, Lime Carbonation, Precipitation
JOURNAL NAME:
Crystal Structure Theory and Applications,
Vol.4 No.3,
July
27,
2015
ABSTRACT: The reaction studied in this work is the synthesis of nanometric size calcium carbonate particles
by carbonation of a suspension of lime, which represents the most common industrial route. It
consists in bubbling carbon dioxide in a suspension of lime to obtain precipitated calcium carbonate
(PCC). PCC is a mineral filler with various applications: sealants, paints, paper, ink, pharmacy,
cosmetics, food etc. However, there is a challenge related to the synthesis and the use of this precipitate:
the agglomeration of the monoparticles. The aim of this work is then to understand the
mechanisms of this phenomenon and to study its kinetics to improve the run of the process and
the control of its impact on the final product. Experiments realized with a high concentration in
sodium chloride (2 M) showed that the modification of the electrostatic environment did not
change the particle size distribution and the morphology of the agglomerates. This indicates that
the electrostatic interactions are not responsible for the agglomeration but the formation of crystalline
bridges induced by the crystal growth. Thus, thanks to an agglomeration model including
the crystal growth rate, the agglomeration kernel β and the agglomeration constant β0 can be determined
using a mathematical treatment of the experimental particle size distributions. Finally,
by varying the experimental conditions, it appears that the agglomeration constant increases with
the temperature whereas there is an optimal value regarding the shear rate.