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I work in a CDU plant. The plant loads two types of crude oil, one of paraffinic type API 48 and other one of naftenico type API 25. When crude oil naftenico is loaded high instability is had in the vacuum system (Loss Vacuum in the Column), situation that does not happen when paraffinic crude oil is loaded. Can it be something related to the ejectores? or to major production of non condensibles when crude oil naftenico loads? . The furnace-outlet temperature is 725°F with crude oil naftenico and 650°F with crude oil paraffinic.
 
Answers
19/07/2010 A: Morgan Rodwell, Fluor Canada Limited, morgan.rodwell@fluor.com
This sounds like the problem is in the Crude Tower - when running the heavier crude, you are not getting all of the Atmospheric Gas Oil out of the Atm. Tower Bottoms. This light material will go straight to the overhead of the Vacuum Tower and overload the vacuum system. You may need to increase the CDU furnace outlet temp, lower the CDU operating pressure or increasing stripping steam in the Atm. Tower.