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Wall Thickness Of A Vacuum Distillation Column


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#1 barley

barley

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Posted 28 March 2008 - 03:40 AM

Hi, I am a final year student. Currently i am doing a design project to seperate a mixture under vacuum condition by distillation column. I am using a pack column with structure packing.
Detail of my design is:
Column pressure: 37.5kPa
Temperature : 200 deg C
column diameter : 2.2m
height of column packing : 10m
Column material : stainless steel 316
Packing type : Sulzer gauze packing

(a) I found hard to get the BS 5500 curve or formula for me to determine the column wall thickness. C
(cool.gif The internal space between my packing section. According to the standard, hight of packing should not more than 3 time of the column diameter. Hence, i divide it to two section. But, what is the best space between the two section for mt to install liquid distributor and liquid collector? Is there any formula to esstimate it?
© How to estimate which type of support grip is best my column.

Can anyone give me guide to get the best approach?



Thanks. smile.gif .

#2 Art Montemayor

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Posted 28 March 2008 - 06:23 AM


Barley:

My response to your 3 comments/questions is:

(a) OK. I don’t know what BS 5500 is; I use the ASME code to determine external pressure effects on vessel walls, and that is hard too.

(b) I use a maximum of 10 to 12 feet of height of packing for each bed in a distillation or absorption column. The “best” spacing between beds is what you require to obtain good liquid re-distribution and safe, convenient access to the tower internals in order to carry out inspections, maintenance, and dumping and replacement of the packing. Use your good engineering judgment as everyone else does. There is no magic formula – just common sense. I normally allow a minimum of 24” between beds.

('c) What is a “support grip” on a column?

I hope this helps.


#3 Zauberberg

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Posted 28 March 2008 - 09:04 AM

I guess Barley was refering to packing "support grid" in his post.

When selecting the type of support grid, have in mind that this device has a huge influence on tower open area and, therefore, on total column hydraulic capacity. You can estimate the overall open area by multiplying support grid open area and packing open area. There is always a compromise between minimizing support grid open area and its mechanical integrity - which is the basic purpose of this item.

One of the ways to battle against potential hydraulic bottlenecks in the grid zone, is to employ a layer (20-30cm in height) of packing with larger open area just above the support grid, and then to switch to more efficient type of packing with less open area and higher contacting efficiency.

I envy you because of this beautiful project you have...
Best of luck,




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