Characteristics and composition of fouling caused by pig slurry in a tubular heat exchanger – Recommended cleaning systems

• Published in: Journal of environmental management 2013-03, Vol.117, p.17-31
• Main Authors: Cunault, C., Coquinot, Y., Burton, C.H., Picard, S., Pourcher, A.M.
• Format: Article
• Language: English
• Subjects: Animal Husbandry; Animal, plant and microbial ecology; Animals; Applied ecology; Biofilm; Biofilms; Biofouling; Biological and medical sciences; Chemicals; Climate change; Conservation, protection and management of environment and wildlife; Environmental management; Environmental Restoration and Remediation - instrumentation; Environmental Restoration and Remediation - methods; Environmental Sciences; Fouling composition; Fundamental and applied biological sciences. Psychology; Gas; General aspects; Heat exchanger; Heating; Hogs; Hot Temperature; Kinetics; Manure - microbiology; Microscopy, Electron, Scanning; Pig manure; Pigs; Pilot Projects; Swine; Temperature; Thermal energy; Thermal treatment; Water treatment; Whitlockite
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2012.12.017

The structure and composition of the fouling deposits caused by pig slurry heated in a tubular heat exchanger were characterized to understand their formation and thus be able to minimize fouling and define effective routine cleaning methods. Two temperatures (55 °C and 80 °C) were investigated. Two types of fouling were identified: organic/mineral and biofilm. The first only formed at temperatures above 50 °C, often during the heating phase, and was the main problem encountered in treatments at 80 °C. Organic/mineral deposits formed a thin compact sub-layer and a thick porous top layer composed of 67–76% minerals, 9–15% proteins, 8–20% carbohydrates and 0–5% fats. Biofilms formed at temperatures between 25 °C and 70 °C in both the cooling and heating sections of the exchanger. This type of fouling predominated at temperatures below 55 °C. The biofilm covered a thin mineral base layer. Strongly acidic or alkaline washing cycle are recommended to clean Type I deposits, while in-line gas-rumbling is recommended for Type II fouling. ► Two types of fouling occur in heat exchangers treating pig manure at 55 and 80 °C. ► Type I is mineral/organic and adheres tightly to the surface of the heat exchanger. ► Type I can be removed by strong acid or alkaline treatment. ► Type II is mainly comprised of a biofilm. ► Type II can be removed in line by gas-rumbling and an acid wash.