Tower Pressure Drop and Flooding 1

[explosiveseng]

Currently reading a couple of texts by Norm Lieberman (A Working Guide to Process Equipment and Troubleshooting Process Operations) to help better understand an ethanol/water distillation column that I'm currently working on.

In the 3rd and latest Ed of Working Guide, p.34, the author provides an equation for determining the best efficiency point (incipient flood point):

(delP)(28)/(NT)(TS)(s.g.) = K

delP = pressure drop across a tray section, psi
NT = the number of trays
TS = tray spacing, in inches
s.g. = specific gravity of clear liquid, at flow temperatures.

Once K is calculated, the value can be compared with other number ranges, based on the authors observations, to determine the column efficiency.

The column is an old bubble cap tray arrangement with 32 trays, each 5 inches (estimate) apart.

The amount of instrumentation is rather limited. The pressure drop from the bottom of the column to the top is 8-7=1 kPa = 0.145 psi.

For those that have used this method in the past, would it be correct to do the following:

*Pressure drop over 32 trays = 0.145 psi

* NT, or the number of trays, is equal to 32.

* TS is estimated to be 5 inches.

* What would be the best way to approximate the S.G. of the clear liquid, at flowing temperatures, if only the bottom (100.5 deg C) and top (80 deg C) temperatures are known?

Thanks in advance for any assistance.

 

[explosiveseng]

My apologies, the pressure drop over the column is 7 kPag (1.01 psig), not 1 kPag as mentioned in my thread.

 

[StoneCold]

explosiveseng
If it was my column... I would just adjust the feed rate up and down and the reflux up and down to find the sweet spot, based on GC shots of the distillate. That being said a bubble cap column with 8" tray spacing is a long ways from what I would call the ideal ethanol column. You might want to consider replacing the trays with packing and reusing the column shell.

My advice, worth what you paid for it.

Regards

StoneCold

 

[explosiveseng]

Thanks for the advice, StoneCold.

I'll have a play around with the reflux ratio at our normal feed rate and see how far I can increase it before the water content in the distillate begins to rise again.

Cheers,

explosiveseng