3 replies to this topic

[Austro]

I am doing simulations in pro/II and have a few questions.

1. Is the pressure of your feed going to be the same (or roughly the same) as your feed tray? My steam that I am adding is at 50psig.. will this have a significant impact on the pressure of the column, or are vapor flow rates generally so high that the pressure of the steam is generally negligible? Is there a good rule of thumb for pressure drop per tray?

2. For pressure suppression of light crude feed, how much pressure is necessary? If there is slug flow, can you just tilt the pipe up (I remember something about this vaguely). Does it still have to pressure suppressed after exiting your HEN?

[mishra.anand72@gmail.com]

May be pressure of feed is roughly same as feed tray.

[Zauberberg]

Hello Austro,

For crude/vacuum distillation towers, feed pressure will basically float on back-pressure from the column. As I stated in one of my posts, it is reasonably to assume 0.005-0.01 bar pressure drop per tray (for packed towers, you can expect much lower pressure drop per stage/packing). Changing feed stage should not affect your feed entrance pressure in these configurations.

Regarding flow regime in heater transfer line (I guess you are refering to the line connecting heater outlet and column flash zone), it should be - and it is in most cases - annular mist flow. BUT, it depends on crude type being processed in the plant. You should be able to check this by calculating vapor/liquid flows and their properties, and performing hydraulic check in pipeline simulation software; or simply do it manually, using existing correlations for two-phase flow.

I don't understand what do you mean when you say "pressure supression of light crude feed". Usually, what you can expect when processing feed that is too much lighter (compared with tower design feed) is that you cannot maintain column heat balance which will lead you to decreasing plant capacity and/or heater outlet temperature - resulting in loss of distillate yields in any way. Can you write in more details about this particular issue?

Best of luck,

[mishra.anand72@gmail.com]

Leave it.