How to calculate weather impact on control unlagged to head.

[jamesbanda]

Dear All,

I am looking for a rule of tumb to calculate if a dont lag (insulate) the top section of a column what the impact on performance would be ?

I am basically looking for a rule of thumb calculation.

 

[ash9144]

If your tower is operating at temperatures other than ambient a good rule of thumb is don't leave it bare. If you are above ambient temperatures it will cost you a lot of money to heat the column to make up for ambient losses also any sudden weather change will likely knock your tower out of specification.

 

[mbt22]

Perhaps estimate a heat loss from the column based on surface area and temperature difference, then estimate how much additional material would condense on each stage, and what it would do to the V/L profile. Hopefully, that might give you an idea of whether more detailed analysis is required. Most common process simulators will have the option of including heat removal from each stage if you want to know what the effect on product qualities is likely to be. I'd just use this as a directional indication, rather than claiming as gospel, as the heat loss calculations are likely to be pretty rough.

The other consideration, as was rightly mentioned by Ash, is the operability. Overhead cooling by fin fans will provide you with a rain detector, cooling improving as the weather gets worse. The same thing would happen to your column, along with changes in wind speed, ambient temperature and the like.

To be honest, I would have a wander round site, look at a few similar temperature/pressure columns and see what's been done there, and a chat with operations to see if it works. A few quick calculations on cost of energy vs heat loss to confirm that what was appropriate is still right now that energy prices have increased, then stick with something that has been shown to work.