40. Heat Exchangers Fouling, Cleaning, and Maintenance

Fouling results in a significant cost to the process and power industry, and a better understanding of the fouling behavior and mitigating measures is of interest to both personnel in operating facilities and research organizations. Fouling reduces the heat transfer rate and increases the pressure drop of heat exchangers. Fouling mechanisms are broadly classified as sedimentation, chemical reaction, crystallization, and biological. Heat exchanger designs should accommodate these fouling mechanisms and guidelines based on the vast operating experience that are discussed. Assignment of thermal margin, expressed as excess area, is one of the most important design parameters. Margins range from less than 10% excess area for light fouling applications to more than 100% for heavy fouling service. Fouling research has focused on understanding fouling mechanisms, predicting fouling behavior and mitigating its consequences. Due to its complexity, development of predictive models has been slow and much recent research has focused on cleaning and prevention technologies. Online techniques to clean heat exchangers have been implemented, but there are no universally accepted techniques. In addition to chemical and mechanical cleaning methods, electric and magnetic fields and ultrasonic/acoustic techniques are used.