EXPERIMENTS AND MODELLING OF CALCIUM SULPHATE PRECIPITATION UNDER SENSIBLE HEATING CONDITIONS: INITIAL FOULING AND BULK PRECIPITATION RATE STUDIES

Crystallization of calcium sulphate, an inverse solubility salt, on a heated surface under sensible heating conditions has been studied. A temperature measurement technique was employed to detect initial fouling rates. Fouling experiments were carried out to determine how process variables such as surface temperature and velocity affect the initial fouling rates of calcium sulphate scaling. Experimental results show that, at a given surface temperature, there exists a maximum initial fouling rate for a range of fluid velocities. Also, this maximum rate and the fluid velocity at which it occurs both increase as the surface temperature increases. These observations are all qualitatively in agreement with the Initial Fouling Rate Model (IFRM) of Epstein (1994). The fouling experiments were supplemented by kinetic batch experiments to make a comparison between fouling activation energies and purely chemical activation energies