Question
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What are the likely causes of and solutions for severe fouling in a vacuum unit’s preheat section?
Apr-2021
Answers
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Celso Pajaro, Sulzer Chemtech, celso.pajaro@sulzer.com
The question is not so clear about the nature of the atmospheric residue and/or the streams that exchange heat with it. These are some potential causes:
- Low velocity of the atmospheric residue in the tubes (it should be above 6 ft/s)
- Leakage in the heat exchanger that allows the hot stream into the residue creating compatibility problems
- Mixing different types of atmospheric residues (paraffinic and non-paraffinic sources) that have compatibility problems leading to asphaltene precipitation.
- Paraffinic residues stored at low temperatures which allow the precipitation of solid wax.Apr-2021
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