3 replies to this topic

[Mahesh@A&M]

In the process of increasing column throughput, I contacted Koch and they suggested Superfrac trays will increase throughput by 130%. Main limitation in capacity is jet flooding above 90% on top 20 trays of the column (high vapor traffic)

On my part, I did rating calcs(chemcad and Koch Glitsch software) and real time trials to find our maximum stable capacity. Based on this data, Koch recommended superfrac trays with VG-0 valves in place of Ballast trays with V-1 type valves.

These trays have more active area due to small deck valves and hanging downcomers.

My condenser and reboiler are well designed for more than 130% throughput. Now how should I believe that these new trays will do the job what the vendor says? Is it at mercy of the vendor?

Appreciate you thoughts and experience in such column revamps.

Thank You

[Andrei]

You can ask for hydraulic guarantees from the vendor, and of course you have to think of a plan how to test and assess the trays performance. It is a common practice to request/give hydraulic guarantees.
Don't limit your options to one vendor, contact others, discuss and see what kind of guarantees they are prepared to give.
I know al least one case when another tray provider, Sulzer, replaced the trays because they didn't hydraulically performed as contracted, free of charge.
As a comment I think Koch offered you a throughput increase to 130% and not by 130%, is that right?

[Mahesh@A&M]

My bad. Yes, throughput will increase to 130%. This column operates at 7 psi absolute.


Thank You

[Zauberberg]

Leaving this job 100% to the tray vendor is the recommended way to go. You only have to be sure that you have provided accurate input data based on which the hydraulic calculations will be done.

I had several occasions during my career when trays/packing replacement has been executed by Koch-Glitsch, and each of these contracts contained performance waranty agreement. In other words, like Andrei says, vendor will guarantee the required parameters of tower internals at specified throughput/conditions.

One additional thing for your concern is to assess turndown parameters of new internals and evaluate them against minimum throughputs which can be expected in your plant. One bad thing with high-capacity trays is that they usually have very small turndown, and if you ever plan to run this tower at very low capacity the new trays can have quite detrimental effect in terms of reduced separation efficiency at lower-than-design throughputs.