Fouling Mitigation for Crude Preheat Train

The pH value has a considerable role in the corrosion fouling rate and the corrosion rate is at minimum for a pH of 11 to 12 for steel surfaces. Low oxygen concentrations in the flue gases promote the fire-side corrosion of mild steel tubes in coal-fired boilers. 

Fouling is a very serious issue for crude preheat train in oil refining plants and it is characterized by the following root causes  

Low Velocity Low velocity can promote accumulation of fouling deposits. The desirable velocity for heat exchangers for the crude preheat train is between 6 and 7 ft/s. 

Salt Removal If salt eannot be removed suffieiently from erude via desalting, severe corrosion fouling could be the eonsequenee. 

To remove the waxy deposits online, block in and bypass the tube side of the fouled exchanger, while continuing sheUside flow, which heats the tubes. After a while, waxy deposits are melted off and harder deposits are spalled off due to thermal shock. After 20 min, restore normal flow. According to Lieberman (1997), this method works well in several cases. 

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