INFLUENCE OF THE FLOW SYSTEM ON THE INHIBITORY-ACTION OF CACO3 SCALE PREVENTION ADDITIVES

The influence of hydrodynamics on the degree of CaCO3 scale suppressio n by anti-scalants was studied by comparing scale formation in the pre sence of inhibitors in two different flow configurations. One system c onsisted of a supersaturated solution flowing as a freely falling film outside a vertical stainless steel tube. In the other system, the sup ersaturated solution was in full flow through a stainless steel pipe. Tests characterizing scale formation and scale inhibition were perform ed with the two systems operated under comparable conditions with resp ect to water chemistry, wall shear stress and temperature. The experim ental data showed that suppression of scale deposition by an anti-seal ant in the falling film system was considerably more effective than th at achieved in the pipe flow system. This rather unexpected effect is rationalized by analysis of the fundamental difference in the mechanis ms of scale formation and scale inhibition in the two systems. Results of this study highlight the possibility that system hydrodynamics cou ld be a parameter of no lesser importance than chemical factors in sca le suppression by additive treatment.