Dear PingPong,
Thank you for such informative post for this discussion. With your information, I have work on to got some help and get information by using ASPEN plus. Here is what I have got;
Physical Property model: NRTL
Azetrope mixture at 1 bar: 60 degC
With;
Water 27mol%, 8.77wt%
iBA 72mol%, 91wt%
Azetrope mixture at 1.25 bar: 66 degC
With;
Water 29mol%, 9.37wt%
iBA 71mol%, 91wt%
Physical Property model: UNIQUAC
Azetrope mixture at 1 bar: 60 degC
With;
Water 25mol%, 7.61wt%
iBA 75mol%, 92wt%
Azetrope mixture at 1.25 bar: 66 degC
With;
Water 26mol%, 8.07wt%
iBA 74mol%, 92wt%
Physical Property model: PENG-ROB
Azetrope mixture at 1 bar: 53 degC
With;
Water 48mol%, 19wt%
iBA 52mol%, 81wt%
Azetrope mixture at 1.25 bar: 60 degC
With;
Water 49mol%, 19wt%
iBA 51mol%, 80wt%
And to answer your question;
Question:
Does the overhead drum (reflux drum) have a water boot to allow separation of free water?
Answer:
The reflux drum does not have a water boot to separate water. I believe the original design does not expect high moisture from the feed. The plant has been running since 9 years ago, until recently we have high moisture.
Question:
1. Is it possible to operate with subcooled liquid in the overhead drum, so as to separate as much free water as possible, or
2. is the column pressure determined by the temperature in the overhead drum? In other words: how is the column pressure controlled?
Answer:
1. No it is possible to operate with subcooled liquid in the overhead as I mentioned earlier the overhead piping use fin fan cooler.
2. Could you explain more on this "column pressure determined by the temperature in the overhead drum". Column pressure controller: In my system, the pressure reading is come from the overhead column piping before going to fin fan cooler. The pressure reading will send signal to 4 valve (split range) according to the split range reading.
I still do not have any solid theory to change any parameter for the moisture, and the moisture still maintain in range 1.45 wt% to 1.5 wt%.
I appreciate for any idea. and thank you in advance.