Four steps solve crude-tower overhead corrosion problems
- Process Improvement Engineering, Metairie, LA (United States)
Hydrochloric acid attack is one of the oldest and best-understood refinery process problems. This would lead one to think that preventing localized hydrochloric acid attack would also be well-understood. Experience, however, indicates that this is far from true. The problem originates with the presence of salt water in crude oils. Most of the salt content of the brine dispersed in crudes is in the form of sodium chloride (NaCl). About 10% of the salt, however, is present as magnesium chloride (MgCl[sub 2]) and calcium chloride (CaCl[sub 2]). In the presence of water and heat, these chloride salts hydrolyze to form HCI. The two-stage overhead system using the hot and cold drum is a design that, despite its widespread use, does not fulfill its objective of stopping crude-tower overhead corrosion. The following program is, in the opinion of the author, the only way to halt overhead corrosion in a crude tower: effective desalting that removes more than 60% of the MgCl[sub 2]; caustic injection down-stream of the desalter to control chlorides in the reflux-drum water draw-off boot; forced water condensation in the crude-tower overhead vapors; and sufficient addition of neutralizing amine to control water boot at a pH of about 6. Finally, there can never be a truly effective replacement for proper desalting. Process Improvement Engineering's experience has repeatedly proven that desalting is the most cost-effective method of controlling hydroscopic hydrochloric acid corrosion. When downstream resid-hydrotreating processes preclude the use of neutralizing caustic, the importance of the desalter is magnified even further.
- OSTI ID:
- 5394822
- Journal Information:
- Oil and Gas Journal; (United States), Vol. 91:27; ISSN 0030-1388
- Country of Publication:
- United States
- Language:
- English
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