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

摘要

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℃and 80℃) were investigated. Two types of fouling were identified: organic/mineral and biofilm. The first only formed at temperatures above 50℃, often during the heating phase, and was the main problem encountered in treatments at 80℃. 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℃ and 70 ℃ in both the cooling and heating sections of the exchanger. This type of fouling predominated at temperatures below 55 ℃. 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.