Internal Condenser Design for column overhead. 1

[AB6005]

Hi all,

Anybody has got a experience in designing of internal condenser to the column overhead.

If so what is the primary criterion to opt for such type of condenser.

Thanks in advance....
Prabhu.

 

[Latexman]

Low pressure drop.

I've found the plots by Dukler to be quite useful when designing condensers. It's Fig. 10-10 in my 6th Ed. of Perry's.

Good luck,
Latexman

 

[AB6005]

thanks for your reply latexman...Colud you be more explanatory on those pressure drop point...my interest of column to which i am going to design works under vacuum.

 

[Latexman]

The main reason condensers are built into columns is low pressure drop. It is integral so there is no piping from the column to the condenser and from the condenser back to the column. No piping yields low pressure drop. Columns that operate under vacuum have the least amount of pressure available, so internal condensers are very common on vacuum columns.

Good luck,
Latexman

 

[sshep]

If the criteria is low pressure drop, then a direct contact condenser is as low as it gets- this is an internal type that used to be very common.

At the site where I work now, there are numberous columns with plate type internal condensers. The condensers are on vacuum, atmospheric, and pressure towers. The justification is cost: gravity flow is used for reflux and (if possible)distillate thereby eliminating pumps, reciever (functionality is done in column), and overhead piping. The drawbacks are maintenance related- an exchanger leak becomes a major repair proposition. An exchanger replacement involves cutting the tower head off in what our site manager calls a column circumcision.

If you want more info, let me know what aspect you are interested in.

best wishes,
sshep

 

[AB6005]

Thanks,
Prabhu.

 

[sshep]

Hello AB005,

FYI, on this site the internal condensers are plate type. I have seem some vertical U-tube installations, but these always seem to have been smaller duty requirements- generally columns that take little or no liquid distillate. Comparing a large condenser with column diameter, you can see the problem of getting lots of conventional bundle area inside a tower. If applicable, an A (preferred) type channel end can be bolted directly to a flange on the top head. I am not sure about mechanical design aspects of the weight of the bundled, etc.

If you have a liquid distillate, internal condensing requires some internal compartment to catch the liquid and manage level- this adds to column height. Reflux (and sometimes distillate) can be taken by gravity so pumps are saved. Cooling water must be piped to and from the exchanger. The pressure of the cooling water system must be sufficient to overcome the hydrostatic head to fill the elevated exchanger for start-up, and the pressure must always stay high enough to avoid boiling water in the tubes. Remember that the exchanger will likely be at an elevation above the cooling tower, so be aware that the cooling water could run under partial vacuum at height if header pressures are low. With plate exchangers on this site the cooling loop is a closed clean water pressurized system (which itself discharges heat to a conventional cooling water system).

Put your temperature gages, extra valves, etc at a level near grade for easy access. Include a vent (recommend an automatic float type) and TSV (must be on exchanger side of any local block valves) at the exchanger. The process design is straight forward, but you are advised to discuss the whole design with maintenance. You are committing them to a crane to service this exchanger, which must be lifted full of water (can't drain the u-tube in situ). In situ chemical cleaning (if you do that with your cooling water) will also require more planning.

best wishes,
sshep