A Review of Crystallization Fouling in Heat Exchangers

Abstract

A vast majority of heat exchangers suffer from unwanted deposition of material on the surface, which severely inhibits their performance and thus marks one of the biggest challenges in heat transfer. Despite numerous scientific investigations, prediction and prevention of fouling remain unresolved issues in process engineering and are responsible for large economic losses and environmental damage. This review article focuses specifically on crystallization fouling, providing a comprehensive overview of the state-of-the-art of fouling in heat exchangers. The fundamentals of the topic are discussed, as the term fouling resistance is introduced along with distinct fouling behaviour, observed in laboratory and industrial environments. Insight into subsequent phases of the fouling process is provided, along with the accompanying microscale events. Furthermore, the effects of fluid composition, temperature, flow velocity, surface condition, nucleate boiling and composite fouling are comprehensively discussed. Fouling modelling is systematically reviewed, from the early work of Kern and Seaton to recently used artificial neural networks and computational fluid dynamics. Finally, the most common fouling mitigation approaches are presented, including design considerations and various on-line strategies, as well as off-line cleaning. According to our review, several topics require further study, such as the initial stage of crystal formation, the effects of ageing, the interplay of two or more fouling mechanisms and the underlying phenomena of several mitigation strategies.

Iterative quality weighted interpolation for LPV‐MPC control of industrial heat exchanger under varying fouling conditions

“…The tracking error is quantified by using the squared difference between the reference/setpoint (T sp so ) and predicted HE behavior ( b T so ) for a finite duration indicated by the prediction horizon (p) as in (10). The change in tube side mass flow rate (m t ) from the nominal value (m SS t ) is determined over the finite control horizon (m) as in (11). It provides inference on the control demands required by the HE to cool down the naphtha to the desired temperature amidst disturbances and fouling.…”

“…10 A higher rate of fluid velocity (Re > 12,000) causes reduced fouling deposition and significant foulant removal. 11 Several experimental studies reveal the direct dependence of fouling deposition on heat transfer surfaces to the foulant concentration in the fluid. 12 Adaptive control strategy is widely investigated to control HE with FR variations.…”

“…For instance, cooling water used in HE tends to deposit salts such as calcium sulfate and calcium carbonate onto the inner surface of condenser tubes, gradually reducing heat transfer performance, surface thermal conductivity, and condenser efficiency, with substantial economic consequences 10 . A higher rate of fluid velocity ( Re > 12,000) causes reduced fouling deposition and significant foulant removal 11 . Several experimental studies reveal the direct dependence of fouling deposition on heat transfer surfaces to the foulant concentration in the fluid 12 …”

A transferable force-field for alkali metal nitrates

“…Nucleation and crystal growth are fascinating phenomena that require computationally expensive tools to be fully understood [1,2]. Recent studies have focused on molecular anion systems, particularly carbonates, phosphates and sulphates, due to their biological and industrial relevance [3]. Alkali metal nitrates are made up of a monovalent cation and a simple triangular molecular ion.…”

Preliminary Proof-of-Concept Testing of Novel Antimicrobial Heat-Conducting “Metallic” Coatings Against Biofouling and Biocorrosion

“…The formation of deposits caused by biofouling on the heat exchanger metal surfaces increases surface roughness and decreases cross-sectional flow area, which leads to higher friction loss in fluid flow ( Kazi, 2012 , 2020 ). Mitigation methods, including surface scrubbing, fluidizing bed heat exchangers, cleaning-in-place and dosing antifouling chemicals, are the main ways to tackle biofouling ( Berce et al, 2021 ). Conventional approaches to treat biofouled heat exchangers by periodic electrochlorination or acid flushes are costly and environmentally hazardous.…”