Mitigation of hard scale deposition using projectiles for low temperature cooling water services

摘要

One of the viable options to mitigate the formation of hard scales in exchangers of water services is to use projectiles as they may exert ample shear to dislodge deposits. Projectiles come in different types in terms of size, material, structure and texture which, in turn, each would have a different impact on mitigation performance. In this study, the deposition of CaSO4 has been studied as hard scale in the cooling water services and desalination units. To do so, the experimental results of deposition and removal rates which obtained by using P02 projectile which is spongy and soft, has been investigated for different injection intervals. The experimental results showed that when the injection interval of using the projectile is shorter then the deposit rate reduces and asymptotic fouling resistance would be decreased compared with the longer injection intervals. In the course of fouling process of anhydrous calcium sulfate, the sintering phenomenon may occur when the surface temperature changes from 85 degrees C to 102 degrees C which takes between 4 to 6 h depending on the fluid velocity and salt concentration. This may lead to hardened deposit layer thus the injection of projectiles may no longer effective to dislodge the deposit layer.