3 replies to this topic

[curious_cat]

I'm trying to debottleneck an atmospheric distillation column which was reassigned from another duty. Its a small diameter (~250 mm)  column and the separation is easy and theoretically needs only ~6 plates.

 

Essentially I've plenty of height but am limited by the liquid / vapor throughput. What sort of packing would give me ample capacity. HETP & pressure drop I'm willing to sacrifice. The available column height is 6 m so even an HETP as bad as 1000 mm would give me the required plates. 

 

Current max Liquid loading is ~15 m3/m2.hr and Vapor superficial velocity is 0.9 m/sec.  My goal is to get both as much higher as I can. I tried out several data sheets from Koch and the best I could do was a 30% increase. But I feel I ought to be able to do better. 

 

Ideas? What's the max throughput people have managed to get in a packed column? Would a structured or random packing work best for these constraints? 

 

Additional data if it helps:

 

Density of Liq = 800 kg/m3

Density of Vapor = 3 kg/m3

Edited by curious_cat, 14 August 2013 - 02:16 AM.

[breizh]

Curious_cat,

You should consider BX packing and get contact with Sulzer .

 

http://www.sulzer.co...ctured-Packings

 

 

http://www.scielo.br...22009000300017#

 

 

Breizh

Edited by breizh, 14 August 2013 - 08:35 PM.

[curious_cat]

Curious_cat,

You should consider BX packing and get contact with Sulzer .

 

http://www.sulzer.co...ctured-Packings

 

 

http://www.scielo.br...22009000300017#

 

 

 

Thanks Breizh! But according to my calculations BX seems already maxed out for throughput at these rates. 

[PingPong]

Sulzer BX packing is a gauze packing for low HETP, not high capacity, moreover they are sensitive to fouling and not really suitable for crude oil. Better try Mellapak 125X or MellapakPlus 202Y for maximum capacity.

 

 

Without more detailed info on tray loadings and properties however it is not possible for outsiders to advice you properly, nevertheless I will throw a few balls:

 

- Consider grids, like Sulzer Mellagrid, Nutter Grid, F-Grid, or KochGlitsch Flexigrid or similar from other suppliers,

 

- As it is only a small column and not much packing is required, consider making your own packing out of stainless steel or 12Chrome, for example use ange irons in rows that are 90 degrees rotated from each other. Spacing of the angle irons in the same row, and spacing of the rows affects hydraulic capacity.

It would look a bit like splash bars in a cooling water tower. You could even use perforated angle irons like in this photo:

Instead of angle irons or splash bars you could consider rows of thick wire mesh grid above each other, rotated 45 degrees relative to each other. Distance between rows, and percent opening of the mesh affects hydraulic capacity. It becomes a matter of trial and error to optimise.

Edited by PingPong, 17 August 2013 - 09:00 AM.