Tutorial: The Chemistry of Refinery Fouling

The chemistry of refinery fouling is well enough understood to mitigate nearly all fouling. The key information required are the location of the foulant, elemental analysis of the foulant, and identification of precursors in the oil flowing through the fouled unit. Most organic fouling is caused by insoluble asphaltenes: on mixing oils, on cooling after conversion, or during conversion (coke). One exception is the polymerization of conjugated olefins after thermal conversion, such as in a fractionator after a coker. Inorganic fouling is most commonly caused by iron sulfide that is the result of corrosion or by sea salts that pass through the desalter. Once the cause of fouling is determined, multiple mitigation solutions can be determined by tracing the foulant precursors to the source.