Population balance modeling of precipitated calcium carbonate (PCC) flocculation induced by cationic starches

• Population balance equation was employed to model the PCC flocculation process.
• High charge density starch resulted in lower collision efficiency, lower restructure rate and stronger flocs.
• The higher the temperature, the lower the energy dissipation rate
• The addition of NaCl did not show effect on the collision efficiency for both starches.
• The collision efficiency decreased with the increase of the shear rate for both starches.

In order to predict and control the flocculation process, it is necessary to develop quantitative model which can describe aggregation, breakage and restructure phenomenon. In this paper, population balance equation was employed to model the PCC flocculation process. Energy dissipation rate was calculated to evaluate the floc strength. It was found, compared to the low charge density starch, the high charge density starch resulted in lower collision efficiency, lower restructure rate and stronger flocs (indicated by higher energy dissipation rate). The higher the temperature, the lower the energy dissipation rate was needed to break the flocs. The addition of NaCl did not show effect on the collision efficiency for both high and low charge density starches, but weaker flocs were formed and more prominent restructure rate was observed at higher NaCl concentration. The collision efficiency decreased with the increase of the shear rate for both starches. At higher starch dosage, lower energy dissipation rate could break the flocs and higher restructure rate was observed.