Growth mechanisms of composite fouling: The impact of substrates on detachment processes

Fouling processes present significant challenges in many industries; understanding these processes is crucial for accurate prediction and planning effective mitigation protocols. Composite fouling is prevalent in many industrial applications, however, studies of these systems are scarce. In this work, we investigate crystallization fouling in composite systems to understand how substrate properties affect foulant growth behaviour. Crystal (BaSO4 and CaCO3) deposition studies were performed in a once-through flow setup. We used high-resolution X-ray micro-computed tomography scanning to visualize the formed crystals. We extracted the distribution of the shapes, frequencies of the protuberances, surface coverage and density of clusters through image analysis. Our results reveal that deposition behaviour depends on complex substrate-foulant interactions. Whereas the net deposition of CaCO3 on a BaSO4 substrate increased with time, significant detachment processes were observed for the reverse case. The increased detachment of BaSO44on a CaCO3 substrate can be attributed to either the weak interaction within the CaCO3 crystal structure or the CaCO3/steel interface. We also observe that substrate properties govern crystal cluster sizes and distribution. The results from this work provide a basis for the development of more accurate prediction models.