flow rate control for acetone reovery 4

[saleda]

Dear all
we try to recover acetone from solid material that is being dried in vacuum tray driers. at min. 600 mmhg and 50-55 deg c range. there are 2 such driers where batches are charged at uncotrollable times. when tem and vac is applied intially high load of vapors will vaporize and our condenser is not big enough to condense intial high rate of vapor flow so much acetone is wwasted. both driers have common vacuum pump with vfd. is there any way that with this condenser that run utility in its tubes at -18 deg c condense all vapors??

 

[rutherford703]

If this is a continuos operation, the vapor load should be approximately constant due to the addition the fresh feed. If this is a batch operation, if you want to recover all the vapor in the solid, you need to have a temperature control system. That means you operate the system with lower initial temperature to reduce the vapor load at the beginning and gradully increase the batch temperature to increase the vapor load at the end.

 

[MatthewL]

Saleda,

You can also regulate the vacuum at the beginning of the cycle via the VFD, as long as only one dryer is working at a time. Several experiments with the vacuum should get you a good starting point and rate of increase in the vacuum. Or add another condenser, that should be cheaper/easier than changing out your cooling system (I think that is what you are proposing).

 

[Uditech]

In addition to reply of Mathews;Please keep lower gauge vacuum at initial stage.Initial air evacuation produce large no. of non condensables.In the presence of this large flow of non-condensables;Overall heat transfer coefficient of Condenser reduces drastically to gas cooling ;may be in limit of 30-40 kcal/hr-deg c-M2.Please cross check condenser heat transfer area-HTA,LMTD and Overall heat transfer cooling for Gas cooling.This may give proposed flow rate of acetone vapor to be condensed.

At lower gauge vacuum ,BP of Acetone is larger,so LMTD shall be more,HTA required shall be less.

This means that evacuation rate is to be set by practically. Air leakage in system need also to be checked before charging batch