It seems to me that you are using the first definition of Overflash (see my message #12). In that definition 5 % Overflash is extremely high.
As I have advised already twice before: Dirty Washoil flowrate should be about 10 wt% on hydrocarbon vapors from flash zone.
Moreover I is not clear to me how you get to the 52 % (is that liquidvolume% or weight% ? ) crude vapourization required for distillate separation as per TBP curve.
Flashed crude feed is entering above 39th tray. The preflash vapors are also entering at this location in a separate nozzle
Crude, kg/hr - [477000 (total vap) - 1200 (water vapor)] + 638600 (liq)
Preflash hydrocarbon vapor - 52280 kg/hr - 5253 (water) = 47027 kg/hr
Hydrocarbon vapor up from tray 40 to 39 = total vapor - stripping steam rate = 128926-43000 = 85926 kg/hr
Total hydrocarbon vapor in flash zone = 477000-1200+52280-5253+128926-43000=608753 kg/hr
Liquid from tray 38 down to tray 39 - 36734.4 kg/hr
Dirty wash oil/hydrocarbon vapor ratio = 36734/608753 = 6%........Is this calculation right?
I am already maxed out on crude inlet tempearture of 370 C!
Edited by NAP, 19 September 2013 - 08:41 PM.